For anyone interested heres the recipe I used to make liverock
Firstly cement and pool salt (make sure it doesn't have any additives) are mixed. I used a small grain pool salt and an off white cement which is very similar to the colour of baserock. Use a ratio of about 2-4:1 of salt to cement, you'll need to experiment to find which ratio you prefer. Personally I like something closer to 2:1. I don't add anything else though sand, oyster shell and various other aggregates could be added. The dry products are mixed together until everythings even all the way through then water added. Be sure to wear gloves.
Only add enough water to make the cement a crumbly, stiff consistency. It needs to stick together but not be so slushy that if you make a hole it's instantly filled in. You should be able to make peaks in the mix without it collapsing back. You'll need to amke a mold for yoir new liverocks, I just spread a layer of salt in a large storage bin and run my fingers through it to make it lumpy rather then falt and shape cement onto it. You can also carve shapes into the salt and place cement into it like a real mold. Place the now wet cement directly into the mold in whatever shapes you desire, then cover over with more salt.
The new rocks will then need to be left for at least 24 hours, you can then check it, if its hard they can be removed from the mold, if its still crumbly leave it for another 24 hours until it's hard. Then allow to sit outside for four days, you can brush salt stuck to the outside off if you want. You then need to release all the salt thats in the rock, amke sure your rocks aren't too thick or the salt won't release. Soak the rocks in the hottest water you can get, though not boiling and replace the water with fresh hot water four times a day. Do this for two days. You can then check if the salts gone by removing a rock from water allowing it to drain almost totally and once the drippings slowed and almost stopped catch the last few drops on your finger and taste it. If it's salty you need to keep up with the hotwater baths, if its sweet your all good.
Then leave the rocks somewhere outside and forget about them. After three or four weeks bring them back inside and start soaking them in water, changing the water daily. You'll need to do this until the pH of the water drops to below 9, low 8's is what your aiming for. Once you see this do another water change and this time leave the water sitting stagnant for 4 days. Give the water a swirl and test the pH again, if it's still in the low 8's the rocks ready to be used. This whole step should take two-three weeks.
This has been taken from a verity of articles I've read and I've put together my own recipe, which should work quite well, from what I've read of other people using it. The whole thing takes about 6-7 weeks but it's not really very hard to do, resisting the temptation to use the rocks right away is the only problem.
