what about concrete rocks?

I was thinking about making a few custom pieces for my tank, does anyone know if there is anything that could be harmful for my critters in plain old concrete?

 

I made my DIY rock out of portland cement and water softner salt. The salt dissolve during the curing process and leave great detail. After a 1-2+ month curing process there completetily tank safe.
Here they were when I made them.


And here is some of them right after I introduced them.



It's really cheap but the tank safe cure time can be a real drag.

 

The only problem I have is being from New England with the harsh winters(snow and ice) alot of the concrete sidewalks etc. get damaged and seems to fall apart easily. I don't know if that will hold true in your case or not but in terms of chemicals leaching into your water column or rockwork becomming brittle and collapsing possibly hurting corals and other livesotck may be an issue!

 

Like Covey I also made Portland rock for my tank, although just a few rocks have been made I can say that there is no issue with being brittle. Do a 4 part salt to 1 part cement mix and you will see some very nice designs. I used this Salt
from any local Hardware store and used this cement


Very easy to mix, I did one rock with 16 cups of salt and 4 cups of cement and is 15pds and very corse just like alot of my live rock. It is still curing {waiting for PH to stay at 8.3} Then I will be able to add it to my fuge.

With concrete in winter it is not the cold directly that ruins it, it is the water that is in the concrete that is turned into ice that expands from the inside and cracks the concrete and since our tanks stay at a comfortable 78* everything is fine. As far as chemical leaching the only thing you have to worry about the the PH of cement and that is why you have to cure it for up to 2 month while changing water every day or so. Once you have your water at a stable 8.3 you can then add it to your tank and start the LIFE process.

 

I made rock myself although I can't find the pics right now. Never heard of using salt. I used crushed oyster shells and pasta to make shapes and holes I wanted.

As long as you properly cure the rock, in my case a few months of 200 gallon water changes several times a week, you should be all set. Make sure once you tank it you seed it with some good real live rock.

I'll see if I can't find some pics.

TTYL

 

JustPhish, the salt is easier to use then the pasta since it will melt away quickly, it leave behind a very porse rock and is very safe. Now Oyster shell are good to use i just did not want that man made look with a bunch of shell sticking out every where. But also a good idea. Pasta though leaves behind alot of particles in the rock even if the water can get to it. Also using the Salt you dont have to do as many water changes, i cure my rock in an old salt bucket since we all have those lying around and have only changed the water 5 to 7 time in a month and my PH is already down from off the charts to 9.0. Just a suggestion try the salt and tell me what you think.

 

I don't understand what you're saying. The pasta is not mixed in with concrete like you are mixing in the salt. It's simply used as a mold just like the sand it's put to cure in. It easily comes off the rock and if you don't feel like taking it out it will quickly disintegrate in the water.

As far as the crushed oyster shell, IMO it makes for a much more porous and natural looking rock then not using it. All my rock is completely covered with mini brittles, pods, etc with all the tiny crevices the shells produce for them to take refuge in. I'd certainly like to see pictures of your rock.

 

Finally found the pictures.









Now I will have to take some macros of the rock with all the critters in it.

 

Hey JP, I'm not sure how/why you use pasta to mold the rock? Can you explain it a bit further?

 

I did this... after you pour the cement a little bit, you throw in the pasta, then pour the rest. After the cement dries the pasta begins to degrade and leaves holes. It was kinda messy for me. I liked balloons and pvc better. After the cement dried, I would drill it with a masonary drill bit. This would actually pull the balloon out after it popped it.