14 marca 2013

The Ultimate DIY Rocks! Guide to making live rock, also ways to make it more porous

Post pochodzi z forum reefcentral.com napisała go panienka o nicku Insane Reefer. Oryginał zdaje się można znaleść w tym wątku. Umieszczam go tutaj aby nie wyparował w odchłaniach internetu, jak to sie czasem dzieje...

v9.0 FINAL VERSION: Aug - 14 - 2008

Hey All,

These are my favorite tips and links so new people can find it all
pretty easy. It is a summation of the most commonly asked questions and
things I have picked up through making my batches. Some I’ve gleaned
from this thread, others I’ve learned from past mistakes and
experiments. I've been making DIY man-made rock or aragocrete off and on
for close to 8 years, though I learned about it from the pre-internet
BBS's back in the very early 90's. Lately, I have even made some money
on my rocks.


This does not contain any information on "Jiffy Rock", the new method I
am working on to produce rock in under a week or 10 days. This only
pertains to traditional rock methods.

I thought I’d pass this info on – maybe save someone some frustration or spark a new idea.

First, good info can be found at these two places - I think everyone who
wants to make rock should read these in full. One of the articles gets
pretty heavy handed with the science/chemistry aspect, the other babbles
on tangents once in a while, but both are worth the read, IMO.


Reef Propagation Project

List of Appropriate Aggregates

Sand - Sand makes cement stronger, so is something you want to add to
your cement. You may also find that sand is a great casting medium and
that you can get crazy shapes with damp sand. Any “clean” sand will work
– look for darker grains which could indicate heavy metals and avoid
these sands. Whatever you choose, keep in mind that the smaller the
grain size, the less obvious it is on the rock, but for sand for use in
the cement, you want a larger particle size, if possible.

Caribbean/aragonite is “best” for adding to the mud, but very hard to find at a reasonable price.

Play Sand is generally fine to use - most play sands will be made of quartz and so basically inert.

Limestone Sand/Pulverized Limestone has gotten good results as a DSB, so
should also work and can be found at some Big Box Stores like select
Home Despot's.

Glass Sand is a new product on the market that is made from recycled
glass - this would also be an excellent choice and might encourage
quicker coralline growth.

Calcium Carbonate for “Feed Mixing” (AKA Aglime, Chicken Grit, Scratch
Sand), comes in a range of textures and grain size – from sand to gravel
like CC. Most real feed or farm supply stores will carry it in some
form, and for less than $4/ #50, but make sure it is the calcium based
stuff and not granite based – it should have a percentage of calcium
printed on the bag – if not, it might not be the stuff you are looking

Dolomite Sand – Same as Calcium Carbonate, just another name (and slight
chemical variation) and is just fine to use - you might find it as
"Aglime" at the farm supply store.

Sand Blasting Sand can also be used (and works really well as casting
sand) and is sugar fine, look for "Unimin" Brand, or any that says it
can be used for filtration – this will be 99% pure Industrial Quartz.

Crushed Coral - AKA "CC". Makes nice, realistic rock with a high over-all calcium content, but it is expensive.

Crushed Oyster Shell - AKA "OS". Any shell will work, but OS is very cheap at feed stores.

Perlite – has a pore structure similar to CC, but much, much cheaper –
great for making light weight rock. It is basically inert, puffed glass.
Make sure that the perlite you choose does not have any fertilizers
added to it – most do not, but a couple do.

Salt - Many thanks to Travis L. Stevens for figuring this out! The salt
of choice is "Solar Salt Crystals", typically found as a Water Softener
Salt. 99% pure salt. Get the coarsest crystals you can find. Solar Cube
can be used, but is sort of chunky - makes nice holes though. Boiling
the "cubes" rounds off the edges and makes nicer holes. Solar Pellets
can also be used, same as Cubes. Look at your grocery stores or
wally-worlds if your local hardware doesn't have what you want.

Rock Recipes

Ingredients are measured by volume, not weight!

Travis’ Original “Salt Rock” Recipe: 4:1 or 3:1 / Salt:Cement

Improved? “Salt Rock” Recipe: 3:1 or 2:1 / Salt:Cement

Ol' Skool Recipe: 1 to 1.5 : 2 :1 / Cement:CC&OS(mixed – or use perlite&shell mix):Sand

Ol' Skool + Recipe: 1: 1 to 1.5 : 1.5 :1 / Salt:Cement:CC&OS(mixed – or use perlite):Sand

I prefer the "Ol Skool" recipe, but I use a variation with perlite.
Makes excellent, porous rock. Keep in mind that even though the original
“Salt Rock” recipes do not have sand listed, your rock will be much
stronger if you replace a portion of the salt with some sand. On the
“Original” recipe I’d use 2 sand and 2 salt to 1 cement.

It is highly recommended that you do not make “Salt Rock”. Salt is
horrible for cement, and over the last 6 months, I’ve had more and more
complaints coming in about failed, crumbling rock, and guess who gets
the blame? Even the “inventor” of Salt Rock, Travis L. Stevens has
written and said he too, has salt rock breaking up. So my advice, if you
want stable rock, is to not use salt in it, or if you just have to even
knowing it is bad, then use it sparingly.

Basic Procedure

Mix dry ingredients together first, excepting salt if used - add tiny
amounts of water while vigorously mixing the mud. Mud should be sort of
“dry” and a little bit crumbly, not wet and squishy – there is a fine
line between the two. A wet mix will not have as many natural voids in
it, be less porous, and will also bind to the salt, making salt release
more difficult.

If you aren't adding salt, skip this next part.

Once you have reached a slightly wetter mix then you think you need,
lightly toss the salt into the mixture, and then mix it very quickly –
the more salt that leeches off the crystals, the more deleterious the
results can be, meaning more chances for your rock to be messed up.

Be aware that a "dry mix" may give the illusion for the first week of
being more brittle, but after a week or two, it toughens up and is nice
and hard.

As you cast your rocks, try to "drool" the mud into place with marble
sized drops. This prevents large solid masses from forming and makes
lots of natural channels within the rock that will allow water to flow
through the rock and seems to allow the rock to kure faster. If you are
making larger pieces, you can scale your "marble" size up some, but
still work at drooling the mud into place.

After you make your rocks, they need to be kept moist and warm for at
least a week or two to achieve the best hydration possible – though 3-4
weeks is best. Many do take their rock out immediately and start salt
release or kuring in 3 days or so, and haven’t reported any bad side
effects, so it is up to you. However, new info is starting to show that
to put your cement in water before the 2 or 3 weeks of age is needless,
as kuring doesn’t really get going until the hydration is starting to
come to a halt (there has to be calcium hydroxide for us to leech it,
and C-S-H is something that forms latter in the hydration cycle). It is
also starting to sound like those who put their rock into the kure bin
too quickly end up with prolonged kure time, so that is something to
think about too. So you can save yourself some effort and money (water
cost money) by letting it sit for a while to let the chemical process in
the cement have a chance at finishing doing what they are doing.
Plastic bags, wet newspaper, wet casting materials and the like will
help seal in moisture. If you think the rock might dry too quickly, mist
it with a bottle or hose every so often.

Molding/Casting Material

Really, pretty much anything that is dry and crumbly/powdery will work.
I've even used stuffing bread crumbles, but that draws bugs while it





A certain portion of the molding/casting material will remain on the
rocks - most of this can usually be removed with a very quick dip in a
dilute acid solution, followed by a good scrubbing with a plastic or
fine wire, bristle brush.

If you use a Rubbermaid type tote/bin, you can easily reuse molding
material over and over again. Line cardboard boxes with plastic to
prevent moisture leak and wall collapse.

DO NOT Wet Salt, if it is used as a mold material - this means when
working with salt, do not add water to the casting box as you would or
might with say clay or sand.

Salt gives a nice dimpled effect on the surface of the rock, but can
wick out the moisture from the rock, making it dry out too quickly. You
can recover and reuse any salt left over, but will notice a significant
lessening of the amount of leftover salt after each casting.

Sand is my casting material of choice. You can really make some nice,
layered rock with sand. Once dampened, it will continue to keep your
rock moist during the hydration phase. You loose very little from the
casting bin, and if you rinse your rock in a tub, you can reclaim most
of what you use.

Coloring Your Cement

There is a lot of interest in creating faux coralline to make the rock
more interesting while we wait for real coralline and corals to
dominate. First let me say that over all, I have not had a lot of luck
with using non-cement colorants. I’ve tried a gamut of stuff from RIT
dye and hobby paint to Kool-aid, and none of these work. Oh, for the
first couple of days, they might look great, but as the kure progresses,
and as calcium carbonate forms, the colors fade out and eventually can
barely be distinguished. By the time these rocks are ready for the tank,
the color is mostly gone. There has been success using colorants made
for cement and grout, but again, these still do fade because of what we
are doing to our rock.

Having said that, I have some other things to say for those still
wanting to try it. Use real cement colorants – I have a couple of
sources listed below.

Sold in small amounts and in rainbow colors - are very cheap and most should be reef safe as well as mostly color fast:




When you are coloring portland cement, make the color several shades
darker than what you are hoping to end up with. You can choose to color
the mud itself when you make the rock (as Walt Smiths' rock company
does), but you will need a lot of colorant to do so, especially in grey
cement. Instead, you can make up a slurry of cement and sand to make a
"paint" of sorts. Use 1 part cement to 2 or 3 parts really fine sand,
made fairly thin and fairly wet and sloppy (like house paint), and use
it to decorate rock with “coralline algae” splotches. I’ve used white
Portland, but I don’t see why white grout or mortar wouldn’t work as
well – you can use grey, but grey needs a lot more colorant to reach a
desired shade. You can use cement colorants to color the cement any
shade you desire. Working with a paintbrush, you can easily replicate
the swirling patterns of coralline. I’ve also used this mix to paint/dry
brush grey Portland rocks to white.

I’ve been thinking about how the colors fade and think I might have a
solution. Fast set cement. With it not really needing to kure, you could
make your “paint” from the fast set, and the best part is that being
impermeable, it should fade very little (fast sets carbonate very little
from what I’ve read). This would be something you could add to the rock
after it has been kured. Then maybe soak it for a few days after the
“coralline” has cured (2-3 days for fast sets).


Now, I will list my tips and tricks, in no particular order.

Tips and tricks

1. Wear gloves when making rock. If possible, don’t let the cement get
on your skin, especially the dry powder. If possible, wear a painter’s
mask when measuring and mixing dry cement; this stuff can really burn
the inside of your nose.

2. Setup your work area in advance; cover surfaces with plastic or old
sheets if needed (like in your kitchen or living room). Fill casting
containers with whatever mold material you are using, or have it
standing by within easy reach. Give yourself walkways if you are making a
lot of rock – nothing sucks as much as trying to create enough work
space after the fact.

3. Think about the weather for not only the day you cast, but the next
few days as well, if you plan on doing this outside. Rain can make a
mess of things…

4. Use Portland Type I, II (I/II) or III – these are known to be safe
for use and make rock with proper porosity. Fast Set cements can be
used, and are in fact great for things like panels or delicate
branchwork, but because of their naturally impervious nature, are not
the best choice for filtration rock.

5. Mix all aggregates excepting salt into the cement before adding
water. Add salt after you have reached the right wet consistency, and
mix it in lightly – the less salt is leeched off the grains of salt, the
stronger your final rocks will be. Water softener salt of the type
“Solar Salt Crystals” works wonderfully (Thank you Travis Stevens!).

6. 1 part cement to 3-4 parts “other” is an acceptable ratio, whatever
you want to mix together is up to you and you should be ok if you follow
the 1:3-4 part rule - each person usually finds a recipe on their own
that works best for them.

7. Work in layers for added dimension. If you lay a layer of molding
stuff in your container, make a few divots in this molding layer first,
and add cement to these first to make lumps on the bottom, you can avoid
flat bottomed rocks. Now lay the main part of your rock, adding molding
material as needed.

8. You can make neat “cliff-face” striations if you take a handful of
salt, and lay it just along the top edge of wet cement, forming a narrow
line of salt along the edge, laying a thin layer of cement over the
salt, and repeating this to form, on the outer edge of your rock, a sort
of cliff that looks to be cut by water action.

9. Anything cast thinner than an inch is likely to break, unless you are very careful with it.

10. Find a nice bit of stainless steel or aluminum wire – 2mm or so in
width, and bend a handle for one end (remember you will probably be
wearing gloves, so bend accordingly). As you cast your rock, use this
wire to poke Lots of little tunnels all through the rock – all the way
through if you can; this will make the rocks extra porous, and give bug
life lots of places to hide and propagate in-tank, as well as allowing
more water to move through the rock. Alternatively, you can cast the
piece, and then poke as much of it as you can – though this way tends to
look a bit contrived. I like the first way better.

11. Once your rock has cured and it has been curing for about a week and
if you made it mixed with stuff like crushed coral or shells, mix up a
weak acid mix and scrub the outside of your rocks with a stiff bristle
brush. Be sure to take proper precautions when working with acid – not
only from burns, but from fumes as well!!! If you only made your rock
with salt and cement, ignore the acid wash, as your rocks might
dissolve, but still give them a vigorous scrubbing - this will loosen
the weakest stuff and get rid of it without shedding it all over your
tank. If you have shells or coral, this can make the surface even more
porous, and clean cement films from shells and the like that might be on
the surface. I use a mixture of 1/2c muriatic acid added to 2c water.

12. You can make “lock together” pieces by wrapping a bit of PVC in
something like tissue paper or plastic wrap, sticking it in the wet
cement of “part a”, and then laying plastic wrap over and around the
fresh cement/PVC, and then cast “part b”, making sure to get a good fit
around the PVC join. I find this works, but I personally have an easier
time if I cast “part a” with PVC set into it, let it cure, then wrap it
well with whatever, and cast “part b”, and I can cast really large
pieces this way.

13. Branching rock/Coral skeletons. Pick PVC pipe a bit thinner than
what you want your final piece to be. Cut into appropriate lengths,
cutting one end flat and the other at an angle. Drill plenty of holes in
the PVC to help the cement stick on. Drill extra holes on the very end
that will allow you to tie the pieces onto the “main branch” with zip
ties. You can bend PVC into believable shapes using heat from either a
propane torch or a heat gun, and a couple of pairs of pliers (use
appropriate precautions). After you have your PVC framework, mix a
thicker blend of Cement Paint (less water, more cement) and paint/dip
the skeleton, covering completely. I recommend hanging to dry, and
dipping several times, using a paintbrush to smooth it out and prevent
weird drips. When done coating, tie a grocery bag around the hanging
piece to preserve moisture and allow to cure 48 hours or more.

14. Think about how corals come to you, as frags and whole colonies, and
think about how hard it can be to attach these in your typical rock
pile. Flatter surfaces and shallow bowls in larger rock shapes can make
latter placement easier.

15. You can make rock “shells” if you want to avoid the rock pile look
altogether and these are only limited to your imagination and size
constraints. You can stuff the cavity in the back of this hollow
construction with cheap $1.99/lbs rock, or whatever you want. I DO NOT
recommend making these with the cement and salt only recipe! Make a form
of some sort (use your imagination), put it in a box that will fit into
your tank (making a rock too big for the target tank blows), and secure
it to one side, or more (for multi-part casts) with duct tape. Line the
rest of the box with plastic. I made my form from plastic grocery bags
stuffed into a garbage bag, with a little air added, and taped that into
the target box. Slowly build the shell wall (adding details as you
wish), filling the box with salt/molding material, until you have the
form covered with a fairly uniform covering of cement. LEAVE ALONE FOR A
WEEK! Cover with plastic if you can. See my gallery for pictures of the
“”Reef Face” or “Nessy”.

16. Frag Plugs. If you have extra cement at the end of the day, make
frag plugs by using a mini muffin pan, and filling with ½in. of cement.
Spray the pan with cooking spray for easier release. These can be put in
a mesh bag and cured in the toilet tank.

17. Hate scraping the back wall of your tank? You can make thin, wall
covering sheets, that can be glued with silicone to the back wall of
your tank. Alternatively you could make shelves along those lines. I
find casting on a sheet of glass covered in plastic works best for this.
Also marking out the actual measurements of the back wall onto the
glass helps to avoid sizing issues. I DO NOT recommend using the salt
and cement only recipes for this application, nor the use of any salt at
all! I also mix this just a little wetter than I normally use. Once you
are setup, just drool the cement onto the covered glass. I tried doing
large sheets, but these mostly were too weak to hold up and heavy. I
find making smaller pieces (12inX12in or so) that abut like a puzzle
work best, and sort of give the illusion of looking at a cracked and
crevassed reef wall. After you cast these, they need to be kept moist
and unmoved for 3 days, 7 days being much better. Believe me. They do.
And you will need to mist them once a day. I just covered mine with a
garbage bag and used a water bottle to mist it. I recommend an acid
wash, as described above, once these have kured for a week.

18. If you make a rock or rocks you don't like, either use fresh cement
mix to add some new bits, or break the rock up and use it as aggregate
in your next batch - no waste is good.

19. The moister you can keep the cement while it cures, the harder the
final rock will be - try wrapping it in a bag, or misting it while it
cures. Supposedly, if you can let it sit for two to four weeks before
starting to water kure, it will dramatically speed the kure time.

20. Dust your molding sand with oat flour for easy removal of surface sand. Thanks Rhody!

21. Mix molasses with your molding sand to give it more texture. Thanks Rhody!

22. Replace up to 1/3 of your cement with “Hydrated Lime” – this reduces
the over-all alumina content of the cement (and boosts the calcium
content) and makes it more resistant to potential “Sulphate Attack”.

Various things I have used and have worked for me for adding details:

1. Cemented Nylon String. Makes realistic tube worm/duster tubes. Make a
thin paste of just cement, and dip small lengths of the sting in. Wipe
excess off between fingers and lay onto the rock in desired figure.

2. Veggie Capsules. These can make little tunnels when laid end to end
in the wet cement, and then covered with more cement. Or poke into
outside edges to mimic polyp holes. Do NOT mix into the cement mix.

3. Nori Sheets. These can be wetted and formed into shapes or rolled into tunnels.

4. Balloons. Both the round and “animal” ones work. I find that filling
them with water makes them stronger. Doubling them up works well too.
Make sure that you can get the balloon out afterward - i.e. leave the
knot sticking out.

5. Cardboard Rolls. Can be cut to form bracing, tunnels or for pillar
shapes. Be sure to use it in such a way as will allow you to remove it
after a few days of kuring. Hemostats work great for grabbing a-hold and
pulling it out.

6. Tissue Paper. The white stuff you find in gift bags. Disintegrates
quickly during kure. You can make little (or big) “salt bags”, that you
can lay into the middle of larger rocks to give more holes for ‘pods and
the like. Can be used to make caves and tunnels. Just use a small bit
of paper, lay some salt in it and twist or tuck the ends – a small bit
of cotton thread could be used to secure the package too.

7. Pasta. Must be cooked “Al Dente” before use. Do not mix into cement,
it only makes a mess and is a pain to get out of the rock as it gets
really hard and crunchy when the rock dries (ever scraped 3 day old
pasta off a plate?).

Kured Rock that the pasta is stuck in...

Use to add spaces in the rock, or tunnels with spaghetti (at your own
risk). Rigatoni adds a nice effect if placed just right. If you use
pasta, you MUST keep the rock moist at all times – if the pasta dries,
it will most likely never come out, ever.

8. Jelly. No, not like PB&J, but those toys, etc made of the product
known as silicone jelly – often comes in wiggly balls. Also fishing
bait worms made of the jelly/rubber. No need to lube them – they will
release just fine.

Things that DO NOT work:

1. Vinegar/acid kuring. Does have its uses, but don’t expect it to kure
your immature rock – it won’t. Acid, as a general rule is BAD FOR
CEMENT, especially porous cement! A weak solution can be used on FULLY
CURED rock to hasten the leeching of the Calcium Hydroxide, but using it
too soon, or using too high of a concentration is detrimental to the
cement. If you must use it, use regular vinegar at ¼ cup per gallon of
kure water, and use it only if your rock is at least a month old or the
equivalent (steam cured, etc.).

2. Bio-degradable packing peanuts/Cheesy-poofs. I can find no way to really use these that is also safe for the tank.

3. Fish food pellets. That was really, really nasty. I don’t want to go there.

4. Uncooked Pasta. As pasta absorbs water, it expands, causing the
cement to fracture and crack – cook it al dente if you really want to
use it.

5. Alka-Seltzer. Doesn’t work. It dissolves too quickly

6. Yeast. Doesn't work. pH of either the mud or the kure water kills the cells before they can respirate.

7. Co2. Adding into H2O will only make soda pop (carbonic acid), and eat
away at your rock, causing fresh, high pH surfaces to be revealed. It
can work, but only under high pressure, or in a dry, contained space
with a saturation of Co2 for the "atmosphere".

Salt Release

If you used salt in your rock, it must be removed before kuring can
happen. Salt will release in warm water much easier than it will in cold
water, and really hot water (150°F) works best of all. Do not boil
cement as temperatures of over 150°F can be damaging to the matrix of
the rock; water boils at 212°F – 150°F is around the hottest that home
water heaters go to, so the hottest tap water you have would be perfect.
Also be careful about “shocking” the cement – cement is a crystalline
structure and sudden changes in temperature (such as using cold water to
refill a bin that was heated) can cause micro-fractures that in turn
can lead to rock failure down the road. Allow warm rock to cool before
putting it in cold water.

Removing the salt will take multiple water changes. It generally takes
two days to two weeks to remove salt, based on factors such as
temperature and movement of the water, wetness of the mud, aggregates
used and density of the cast piece.

If you aren’t sure that the salt is gone, you can do a “Taste Test”.
After draining and rinsing the rock (pick your largest/thickest piece),
allow the water to drain out for a few minutes. Pick the rock up and use
your finger to catch a drip of water from the bottom of the rock and
taste it. If there is still salt present, the water drop will be salty.
If the salt is gone, the drop will taste of mineral water and very
slightly sweet.

Rock Kuring

Kuring your rock is the next hurdle. It is really, really best to leave
your rock alone for at least a week before starting this step. According
to Quikcrete reps, it takes at least 7-14 days for the rock to stop
curing/hardening (though this process is actually going on for a lot,
lot longer) - even though it looks and feels done. Testing standards say
it takes 28 days to reach full strength and before testing for
commercial applications can commence. By putting your rock in the kure
bin too soon, you are wasting a lot of water, prolonging the hydration
process and making weaker rock. Rocks during this 2-4 week period will
naturally loose pH - from 12-13 at casting time down to 9-11, with NO
WATER USED. I have been finding that by leaving the rock alone for a
month or so, my average kure takes less than 2-3 weeks (and a lot less
water and effort!).

Kuring is pretty straight forward. Lots of time, and lots of water
changes with adequate water volume, unless you have access to a
reasonably clean, free flowing waterway. This step is dramatically
decreased if you wait until the 4-5 week range of your rocks life.
Powerheads help force water through the rock and help the insides kure
out. Adding heat to the bucket, upwards of 90°F will really speed things
along, and if you can get it to around 150°F, it will happen even
quicker. It is much like mixing sugar into tea. If you put sugar into
iced tea, it can be almost impossible to get it to dissolve, but you can
add the same amount of sugar to a cup of hot tea and it almost
instantly dissolves. Same principle here. The cooler your kure water is,
the longer it will take the rock to kure.

Some people have asked if there is a difference in what you kure in, SW,
RO, RO Waste, Tap. For the most part, you just want to use plain tap
water or rain water. RO is fine, if you have it, but doesn’t make that
much of a difference. I would like to give a word of caution for those
wanting to use their RO Waste Water. RO Waste Water is full of heavy
metals and other things we don’t want in our tank, so why would you put
something porous in that and then after it has soaked up all the bad
stuff (like an oil spot on the driveway), don’t you think it will slowly
release those things back into the system? You might as well fill your
system with tap water. That being said, many have used RO Waste Water to
kure in and claim no problems with it. But if you have a hard time
kuring your rock and you are using RO Waste Water, check the pH of it
before using it – if it is higher than 9 or 10, then your kure tests
will never read lower then that, so at that point start using tap water.

When your bucket kured rock quits leeching out scum on the surface of
the water, and stops leaving a white residue on the bottom of the bucket
and on the rocks themselves, you can start checking for pH. Rock has
been known to kure in as little as 2 weeks, but most bucket/bin kured
rock takes 6-8 weeks to reach safe levels – some will take up to 3
months. Be prepared to wait.

When your tests indicate that the rock might be done, you will want to
do a proper pH test on it. To properly test for pH, use saltwater –
saltwater is preferred since this is what the rock will be sitting in
for the rest of its life. Feel free to use old water from a tank change,
just test the pH prior to use. Let the rock sit in this for 3-4 days
without air or powerheads – you want still, stagnant water for this.
After the 3-4 days, give the water a bit of a stirring and check pH with
appropriate test kit. If it is in the acceptable range of 7.0 to 9.0,
it is probably safe to use. If not, continue to kure.

You can use any acceptable pH testing method. The test you use should
have a testing range of 5-10 at a minimum. I like using Litmus Paper. It
can read pH from 1-14, and is fairly easy to read. Litmus paper can be
gotten at “Hobby Lobby” for $3.89 per 100 strips. These can also be used
to test your reefs’ pH Litmus can also be found at pharmacies, online,
and at other full service hobby stores, usually in the section that has
things like “Magic Crystals”, and horseshoe/bar magnets – the “Science

Once kuring has finished your rock can be used

If added to a newly established tank, you can go ahead and put it all in
at once. If the tank is older, with inhabitants, you may wish to add a
rock or two at a time, to allow the system to “settle” between each
addition. Maintain pH testing for the first two weeks and buffer if

Expect an algae bloom.

A few people, those who either have waterways to kure in, or those with
really butch systems have reported no algae blooms, but I suspect they
are the exception, not the rule. If your tank blooms, don’t panic. Most
tanks bloom within the maturation period anyway. Double check your
system for things like NO2 and NO3, and other algae causing symptoms and
correct anything that isn’t up to snuff. Take all the normal steps to
curtail the growth, but then just ride it out. If the bloom is caused by
the rocks, the algae will soon deplete the readily available nutrients
and starve itself out. If it doesn’t go away within a few months, then
you should check into other reasons for the bloom.

If you place your rock in tank with low light for two weeks to a month,
you can avoid most of the bright green covering algae – low lights allow
the rock to settle in without being attacked by algae so badly, or so
it seems, IME…


And in conclusion, I'd like to address expectations. I have a feeling
that some people are expecting the rocks they make to be as hard as
cement blocks or cement stepping stone, because, after all, they are
made with cement, so it should be, right? Well, in this case, no - they
won't be.

Let's compare our “mud” to a typical cement poured “slurry”.

First, poured commercial slurry's are made with a higher ratio of cement
than we usually use. Next, they add enough water that they can pour the
slurry - much like a milkshake. I've never been able to pour my mud; we
try to make ours as dry as we can and still have it stick together. Now
take a look at the aggregates - they use dense sands and gravel, we
usually use calcium based substances when we can - there is a marked
difference in each of these as far as strength goes.

And finally, when cement is poured, they try to get it settled down -
they drag tools over it to smooth it and make sure it is even and all
that, and sealing the surface. We go for as much openness as possible,
and we try not to pack the mud if we can help it.

Looking at it like this might help people come to a better understanding
of what a reasonable expectation of their rock might be.

Our rock is going to flake and shed. The more porous the rock is, the
more likely it will be to do so. The better the mud is made though, the
less you will see of it. Maybe you have seen a box of real live rock
just after shipping. If you have, you probably noticed the rubble in the
bottom. Most distributors are not in the habit of making up the extra
weight in a box with rubble - that would be bad business. Most of that
rubble simply came from the rock during shipping. Calcium based rock is
not the strongest in the world, and essentially, our rock is calcium

But flaking and shedding are not the same as brittle rock. Your rock is
brittle if you can snap large pieces off after a month or two. Small
bits rubbing off is not necessarily indicative of failed rock, those
could just be pieces that didn't get adhered well.

My first piece of advice would be to wait. It takes a month for the
curing process to reach near completion and the rock to reach something
close to its final strength. If your rock seems brittle or flaky, beyond
what you should reasonably expect, just leave it alone for a month, in a
moist (not wet), warm environment, like a plastic bag. Some of the
early salt rock I made seemed really brittle, too brittle to use,
certainly, for the first couple of weeks. It was when I later found it
again, in the bottom of a bucket outside, that I realized how nicely it
had hardened up. If after leaving it alone, you can easily snap sizable
portions off (golf ball sized?), then you have a problem.

My next piece of advice would be to use a stiff bristled brush, like
what you use to clean your grill, to give your rock a good once over
when it reaches about four weeks old (or after the pH test in Jiffy
Rock). This will remove about 90% of the shedding and flaking, if the
shedding and flaking isn't due to rock failure that is. If you have done
this and a couple of weeks later it is readily shedding again, then I'd
say you might have a problem.

Remember that even slight variations can make a huge difference.
Humidity and Temperature at casting and during the cure can make drastic
differences. A tablespoon of water can make a difference on smaller
batches - too wet and too dry can be a fine line. Differences in the
cement itself can wildly vary - every plant uses its own recipe to make
the clinker. Differences in local materials used for the recipe can
often vary with availability and cost. My white cement is going to be
different then Neptunes' cement, and his, even from the same plant as
Sunkools' may vary as well, from lot to lot.

Salt can mess up the strength of your rock, so if you used salt, think
about that. If you added it upfront, with the aggregates, you may have
over-mixed it and too much salt mixed into the batch. Try adding the
salt after the mud is mixed and ready - and just lightly mix it in.

A ratio of 1:3 to 1:5 is best for us. 1 part cement to 3-5 parts "other", which can include salt.

And finally, realize that even the best made rock can still chip and
shed once in a while. Moving it around in your tank, bumping it against
each other (esp larger pieces), will inevitably cause bits to shed or
chip off, unless you went for rounded ball like shapes, which seem to
loose less, but also seem less porous and less attractive too.

I hope this helps a few people out there. I know that having something
you worked hard on, that doesn't turn out like you wanted, can be
disappointing. Hopefully this will help people understand what they
should expect, and what they can do to correct it...

Well, I think that about covers my repertoire. I apologize for the
length of this post, but hopefully some of you will find something of