The Ultimate DIY Rocks!

[sunkool]

the salt disolving in the cement is not going to hurt the rock for the what we are doing. Yes they say the salt weakens the portland but they are talking on a structural level as I said before we are not building houses here.

[reefnewbie54321]

i had kept updated with this threda for a long time but i havny been logged in for months ... i was skimming through and it was talkingabout baking your rocks? is this required for any reason ... i alreday made my firts batch with 2-3 parts salt and 1 part cement and they have been drying for 3 days now....should i bake them for any specific reason other then quicker drying or can i put them in the river behind my house?

[medic29]

the baking is somewhat an experierment to see if we can speed up the process. Yes, you can still put them in the river...

[Insane Reefer]

"They" are cement chemists and professionals...
Salt acts as a desiccant within the cement, removing "pore water", and ends up messing up the matrix of the cement in a very fundamental way, to put it simply. Salt tainted cement has a tendency to crack, craze and disintegrate over a few years time - a lot worse than normal, traditional rock made with no salt can eventually do.

I'm sure I'm not the only one that has notices that the number of people complaining about brittle rock has decreased since mixing the salt in was recommended to be done last. I certainly noticed a difference in friability and over all strength.
And you aren't the only one to say it - but why take a chance with adding the salt too early, knowing all that?

[Insane Reefer]

Originally posted by medic29

On a slightly different note, the first batch of rocks I made several months ago (not the baked ones I talked about above), I had them out sitting on a table in the sun for several days, then last week I put them in a container and filled it with water; I wanted to see how they would affect the pH; when I checked the pH today with my new test strips I tested out at 7. I'm wondering if these rocks are finally ready to go into my tank?

Is there a way to test to find out if anything is leaching out of the rocks or is the only test we can do is watch the pH? Any ideas??

Did you do any water changes on this rock, Rick? A kure other than just sitting outside?
Anyway, stir that test container good, but if it still reads 7, and your rock has been in for a week or so? I'd say you are good to go.

A few people have been trying the air kure (I have a few more pieces too), and seems that air kuring might be almost as effective as water kuring.
More tests should be done - it would be nice for the traditional methods if you could get as much kuring by just leaving it alone as you would by wasting effort and water. Though you'd still probably need to flush some crud out, but a few water changes are better then a lot of water changes...

Unless you have access to a lab, and people who know how to use all the stuff in it, we are pretty much limited to the same things we test our tank for. Might want to test for Phosphates or Silicates, if you have them handy, or if your LFS will do the tests for you (some will, some may charge) - those might be interesting to see, but it is pretty much that or the "chuck it in and see if crap lives or dies" test...

[Insane Reefer]

Originally posted by medic29
IR - has anyone thought about the idea of putting some of our rock in a big preasure cooker, like the ones used for canning? Would this be of any benefit? Someone mentioned the use of pressure during the process.

Michealalan I think it was, on another thread, said he had a friend who offered to autoclave a piece for him.

A pressure cooker would be awesome - would cook the rock just like the brick places do, but a home cooker would be too small to make it worth while - each rock would need 6 hours or so, and the cookers I have seen might hold 2 or 3 small rocks at a time...

[BOKER420]

My big rock pictured on the last page is actually at most 2-3 inches thick in any one place. I used a crock pot bowl upside down in the middle to give it a dome affect on the underside to take up space.

I just wanted to make a few big pieces because thats usually what I buy and I've spent 250-300 dollars on one piece of live rock a few times so a little more time spent on dispersing the salt out of the monster will be well worth it.

I'll have to try and make some smaller pieces now that I have the big ones out of my system. I found a big plastic serving tray that is shaped like a clam that I'm going to try and mold off of.

So if you were talking smaller rocks lets say 10lbs and less. What would be the amount of time it would take before they were good to go into a running system?

Insane,
Is the rock you sell the LFS's always ready to go into someones tank or do you sell it as uncured?

[sunkool]

Originally posted by Insane Reefer
"They" are cement chemists and professionals...
Salt acts as a desiccant within the cement, removing "pore water", and ends up messing up the matrix of the cement in a very fundamental way, to put it simply. Salt tainted cement has a tendency to crack, craze and disintegrate over a few years time - a lot worse than normal, traditional rock made with no salt can eventually do.

I'm sure I'm not the only one that has notices that the number of people complaining about brittle rock has decreased since mixing the salt in was recommended to be done last. I certainly noticed a difference in friability and over all strength.
And you aren't the only one to say it - but why take a chance with adding the salt too early, knowing all that?

Again these chemists are looking for structural support and I could see where that would be an issue. They were not making liverock.
These rocks are not brittle and the rock is only going to get harder every day once put in the tank. The rock will absorb calcium from the water and be covered in coraline way before it has time to disintegrate.

[Insane Reefer]

Originally posted by BOKER420
So if you were talking smaller rocks lets say 10lbs and less. What would be the amount of time it would take before they were good to go into a running system?

Insane,
Is the rock you sell the LFS's always ready to go into someones tank or do you sell it as uncured?

10lbs should kure in 4 weeks or less, if there is good movement.

Mostly it is unkured - I drop the price by 50 cents a pound just so I don't have to mess with it...

[Insane Reefer]

Originally posted by sunkool

These rocks are not brittle and the rock is only going to get harder every day once put in the tank. The rock will absorb calcium from the water and be covered in coraline way before it has time to disintegrate.

You do it like you like
I've seen MMLR that went wrong long after it was added to the tank, and it didn't have salt in it.

But I'm sure you'll be fine.

If you'd like, I can link a few pdf's of research done on cement in saltwater - I think you would be surprised to find that it may not get harder everyday...

[Rhodophyta]

Originally posted by sunkool
Again these chemists are looking for structural support and I could see where that would be an issue. They were not making liverock.
These rocks are not brittle and the rock is only going to get harder every day once put in the tank. The rock will absorb calcium from the water and be covered in coraline way before it has time to disintegrate.

"Structural support" is important to us too, unless we would be happy with live sand or live gravel instead of live rock. And if you've ever watched them build a highway or sidewalk, the structural support of concrete comes from the prepared ground and from steel rebar and grid.

I don't think there is any reason to imagine calcium being absorbed from the water by our rock. Unless we interrupt that process, the calcium in the rock is going to absorb the water of hydration if it can, something it does better in air and humidity. We are concerned with calcium leaking OUT of the rock, raising our pH.

[sunkool]

you are using this rock as a filter and you think ti wont absorb calcuim?

[dngspot]

I have been using concrete rock for about 3 years. I love the stuff. I started with 40 lbs of Figi, I then made 300 lbs of concrete. After about a year it became difficult to tell what was concrete or Figi, except for the arches tubes and caves. The white rock is new rock made for my new tank, I just moved into a 210 rr.
I use 1 part cement, 2 parts pulverized limestone, 2 parts crushed oyster shell.

[Insane Reefer]

Very Nice Dngspot
What recipe do you like to use? Is your rock made with white portland, or just 'white' by comparison?
You of course probably made the bulk of your rock without salt? Do you find that the MMLR is harder to keep 'clean' than real rock? You know - does it collect more crud that you have to blow out, than the real stuff?
I'm always interested in peoples' long-term results. So many folks get out of this hobby after less than a year, so it can be hard to collect data for longer usage...

[dngspot]

The cement is standard portland 1. 1 part cement, 2 parts of pulverized limestone and 2 parts crushed oystershell. After the stuff is cured it looks light grey, when it is put in salt water it is bone white.
I have never cleaned this rock, or blowed out the surface.
Yes I did not use salt
Here is a blury image of a tube.

[Insane Reefer]

Originally posted by sunkool
you are using this rock as a filter and you think ti wont absorb calcuim?

LOL.

That's like saying an air conditioner absorbs O2...

Sunkool.

You are correct that since the rock will be in calcium rich water, that some of the calcium will be 'absorbed' by the rock - so will all the other things in the water, but sitting in the water and being filled by it, and actively removing calcium from the column, are two completely different things.
Our rock isn't going to remove calcium from the tank - unless you are counting the coralline algae using it up as it covers the rock.

If we have made our rock correctly, the process after hydration that occurs is 'cement carbonation', a process where-by free C02 converts the calcium hydroxide (high pH) to calcium carbonate (low pH). But this doesn't mean it has become a calcium sponge. Nitrates? Maybe. Calcium? No.
Just like our rock isn't going to add much in the way of calcium back to the tank. Water has to be very acidic to breakdown calcium from a calcium bearing source - our tanks do not get that low - hence the use of Calcium Reactors.

[Insane Reefer]

Cool, Dngspot

Have any future rock projects planned?

[SilverOne]

sunkool,

Your rock looks great! Do you mind sharing what type of portland cement you are using? Also, what kind of sand?

[dngspot]

For curing rock I use a trash can that is hooked up to my ro waste water. I then drilled a hole in the top and installed a 1/2 inch barb fitting and siliconed it in place. I then attached a hose to it and put it in a floor drain. The hose from my ro sits on the bottom of the trash can. As the new water fills the bottom the old water exits the top and to the drain. It still takes 2 months to cure but I do not have to make the daily water changes.

[dngspot]

Originally posted by Insane Reefer
Cool, Dngspot

Have any future rock projects planned?

I am putting on a demonstration next week for our local club.

[sunkool]

Originally posted by SilverOne
sunkool,

Your rock looks great! Do you mind sharing what type of portland cement you are using? Also, what kind of sand?

I am using whit portland made by Rinker cement. The msds says portland cement and ti dioxide (to make white) same stuff that makes pvc white. I will upload a pic when my video is done uploading.

[Insane Reefer]

Originally posted by dngspot
I am putting on a demonstration next week for our local club.

Awesome
This make a great group project/money raiser, I think.

Have fun with it

[mr.wilson]

1) Salt doesn't mix with cement in theory or practice.

If you use water softener salt or fine or medium salt, it will dissolve the cement and make it very difficult to form or set. The hydraulic process is a chemical reaction that cannot take place in the presence of sodium chloride (salt).

The use of large crystals of raw salt (not reconstituted water softener salt) will only release small amounts of sodium and chloride ions, providing the mix is relatively dry and the salt is added late in the mixing process.

I tried using fine salt in my cement mix and it was like watching a milkshake quickly melt. The more you work the cement, the more it goes to mush. Even though we are not looking for great structural strength, the chemical reaction cannot be impeded, or the salt may dissolve in time.

2) Cement mixes and calcareous rock will not absorb/adsorb calcium or carbonates, other than what is used to build tube worm structures and coraline algae.

Cement-based rock will only absorb phosphate & silicates. This process will remove some calcium as it forms calcium phosphate.

3) Dry curing the rock for the required 30 days, greatly shortens the wet cure time (30 days dry = 60 days in water). Dry curing drives the moisture out of the rock, stabilizing PH in the process.

4) Calcium carbonate has a high PH, not a low PH as stated in a recent post. I won't mention names.

5) Rock will not absorb, or hold nitrates, just phosphate and silicates.

6) Here are some before and after (7 months) pics of a tank with faux coral end walls made of quick setting (polymer-modified) hydraulic cement and oyster shell. You can see the colour change as coraline algae populates it.

The rock used was dead Fiji rock with very little in the way of unique shapes. Most of the DIY rock in this thread looks much nicer. I used a wetter cement mix with less aggregate to bond the rocks together.

While the tank has progressed well, my photography skills haven't gotten any better.

End wall with closed loop intake concelaed before



End wall with closed loop intake concealed after



End wall with closed loop returns concealed before



[i]End wall with closed loop returns concealed after[i]



End wall before



End wall after

[mr.wilson]

Here are some full tank before & after (7 months) shots. To put it into perspective, the tank is 96" long x 30" wide x 36" high.

Full tank shot before



Full tank shot after



Full tank shot (flip side) before



Full tank shot (flip side) after

[sunkool]

Here is a video of diy rock made a year ago with salt mixed in before the water was added. The only thing diffrent is it was made with white tile grout. (white portland and sand pre mixed)
If this is not strong enough for what we are doing then nothing is.

Mr.Wilson
Nice backroud.
I did the same in my tank 2 years ago. again adding salt to the mix. I also added crushed oyster shell.

I guess according to Insane Reefer its time is almost up.

Nope just checked it and its still hard as day one.