Some Man Made Dry Rock

So I still haven't found a buyer for the tank, which is THIS THREAD

 

Here is a quick pic I took of the rock in my 70g rubbermiad stock tank. It looks like I actually have more like 3 large pieces, not just two.

 

what was the recipe you used? I've never read of this happening to anyone, really.

 

For this, all I used was the oyster shell and type II portland cement.

 

I did a 3:1 oyster shell to cement mixture. I made it in very small barches at a time adding water super slowly because apparently it is easy to overdose the water. I used an old 22oz. (650 mL) cup. Three cups oyster shell, one cup type II portland cement, and about 500mL of water poured in slowly while mixing. I would mix about two of those batches to go into each "rock". My understanding is the curing process is really important (I have bever worked with cement prior to this so I just did what I was told). Need to let it fully dry/harden slowly. I just laid a moist old towel on top (I read to use burlap but I didn't have that) and let it dry out. I did this in the middle of winter inside, so there wasn't much of a risk of it drying out all that fast. After it hardened fully (I was able to make about a rock a day with my setup since I only had one mold - a tub filled with wet sand), which I allowed about two weeks for the "youngest" rock and about three to four weeks for the "oldest", I put them in a tub of RO/DI water. That water jumped in pH fast. The longer you leave it in the more lye seeps out. When I let it sit for two weeks (went on vacation), it actually started to precipitate in the water. I would also add some muriatic acid from time to time just to cut down a bit on the costs of water changes. A splash of that in about 70g of water would drop the pH enough for about 48 hours. It would probably end up being cheaper in the long run (and if not cheaper, just a hell of a lot more convenient), to do that for maybe two to three weeks initially and then change the water. Once your water's pH is no longer effected by the rock soaking in it (I allowed 24 hours), you are good to start seeing with life in your tank.

 

I will try and find the thread where I got this recipe on RC. It's been a while since I posted in that thread, and I should probably get some pics of the aquascaping up there to show off my hard work. FWIW I believe the recipe was recommended by a guy who makes coral sculputers for a living for large public aquariums. He says the initial curing process is key. Again, the cement on bought specifically for making this rock was my first ever experience even using cement, so I just followed what the "experts" said to a "T" LOL