what about concrete rocks?

The pasta is used to make different patterns in the rock. For exampple, manicotti can be used to make tunnels that go all the way through rock, or half way, or however you want it to be. Just make your mold design in the sand and then put in the manicotti and pour your mixture around it. When curing in water the pasta softens and comes right off.

Jumbo shells are great for indentations, small caves. Etc. Just gotta use some imagination.

To make myself some tonga branch looking rock I took flexible tubing and pressed it into my sand mold in all sorts of squiggly lines. Poured in my mixture and instant branch rock.

I made myself a nice large flat rock to make a cave. Stuck a broom stick handle deep into my sand mold and then filled each hole with mixture to the top to make a nice flat piece with legs.

Now I can use those legs to hold the rock up off the sand and make a cave where only the bottoms of the legs actually touch the tank or sand bed.

 

This is all very helpful- it is apparent that the concrete is safe for the tank critters as you guys seem to be sucessfully using it already- is there anything in particular I should look for on the bag or just run of the mill cement? Also after apropriate drying time do you think it would cause any fluctuations in my water chemistry as I am only looking to make a few special pieces to suppliment the live rock I already have?

 

Very cool idea using pasta. Thanks Matt and JP for that info. If I ever have the need to make my own rock, I'll keep that method in mind!

 

The best part of the salt and portland recipe is that you don't need any forms. If you notice the rock on the pinic table are free standing. The dryer I mixed the cement the nicer the rocks looked too.

I might make a second batch and use one of those hagen sugar frementor CO2 set up to cure the rock with almost zero water changes.

I saw alot of good ideas after I made my first batch I might sell my first batch a make a second with some real crazy looking rocks.

 

You guys have inspired me to give it a try- I am wanting to do something with Montipora similar to this garf page a friend was showing me-
GARF'S PLATE FORMING MONTIPORA
check it out and tell me what you think.

 

I can't see that being an advantage over just purchacing live rock, except for maybe the shapes you could make, having to cure it for 2 months and do water change daily. But then again, I'm not all that intellegent a person.
Or do you mean cure it in fresh water? I bet that's what you mean and it wouldn't cost so much. See, told you I wasn't that smart.

 

I guess what I had in mind originally was a specific shape- if I add much more rock to my tank I won't have room for water- lol

 

It's a huge advantage over live rock as far as expense. Yes the curing would be in freshwater but I suppose if you really wanted you could spend the money and do it in salt.

You get rock with the exact shapes you want. It's guaranteed pest free. It will cost you like $20 in materials for a 20lb bag of crushed oyster shell and 80lb bag of portland cement.

 

I have used aluminum foil in a crumpled ball to create little pockets in the rocks facing and blow up a little balloon and use them as a mold to create a cave then after the cast is set pop the balloon and you have a good cave or arch. I use crushed oyster shell and it worked great . Also i have pushed nail into the wet set and wiggle and remove to create alot of little holes into the rocks. then a vinegar soak and several freshwater soaks and rinses and in a few weeks its good to go.

I helped a friend to make all of his Rock for his 90 reef and its still running well I have made and used a few flat curved pieces to create a shelf to wrap around the corner overflows to set stuff on..never a problem. Pretty much what justphish used.

 

Tangster i would be careful using Aluminum foil to make your rock. A little piece can get stuck to the hardened cement and make it into your tank where it will leach out toxins that are harmful to coral and fish. The ballon idea is a great one which i have used.

As JustPhish mentioned this only cost about $20.00 if you use oyster shells. Making around 100lb for 20 or My suggestion 4 parts salt and 1 part cement. You will be able to make 400 pounds of rock (1 90lb bag of cement, 9 40lb bags of salt)for just under $40.00. That is .10cents a pound. No where in the world is it that cheap. Even if you have your own boat and gear to dive. The cost of diving will set you back what a few grand.