Ok this is what I used. (Im not taking credit for it as I learned how to make it from various sites and forums)
Crushed Oyster Shells 1bag 50lbs = approx 12$
Water Softener Salt Pellets 1bag = 5$
General Use Cement 1bag 90lbs = 20$
(This is the smallest size I could find)
With these three you can make like a ton of rocks...
The formula = 5parts Shell, 1part Cement, 1part Pellet
The pellets need to be broken into smaller pieces. What I did was break them into three.
You mix it together in a bucket. I mixed it before adding water. I suggest your wear gloves because cement is very basic, and the shells are sharp.
Then you put water in to the point that it is just mushy but not runny. If you have a hose that has the "mist" function that helps.
Have a rubber container and fill it with sand. The sand I used is the same sand that I will put into my tank. From my research, it is not recommended to use the play sand that you find in any department store as it may contain stuff that you dont want in your tank.
Mold the shape of the rock that you want in the bucket. You would have to add water so that it stays in place.
Drop the mixture into the mold.
The salt pellets are used because they dissolve in the water. Whereever you have salt pellets will be a hole afterwards. So you can be creative.
Afterwards you have to let it cure for weeks. This is done by putting it in a body of water that has lots of flow, doing PWC every so often. (I have mine in one of those pond things in my backyard atm) This is because cement is very basic. The PH will be really high. You need to cure it until the PH is that of normal tap water. Adding vinegar helps. Check PH every week.
After you think its ready put it in a bucket of water for a few days, but do not airate the water. Test the PH to see if the rock raises the PH.
Some people soak the rock in an "acid bath" like vinegar before putting it in water. But I didnt do this because i think that it will weaken the rock by doing that right away, so I will be patient and let the water do the curing.
I would like to add that making this rock will save you money but does not replace LR. LR is very very porous compared to this rock. You will still need some LR. Benefit to this is that you can create your own shapes and save a few dollars because eventually this rock will be seeded with the LR in your tank.
