So I saw the website
BioRock. He uses solar panels to electrify a frame with 4 volts or so. The minerals in the water plate the frame. After a base coat, he affixes coral frags on the frame. With the continued electric current in the frame (steel rebar), the coating continues to thicken (~2 inches/year) and the corals even grow faster and are more resistant to temperature fluxuation.
So my plan is to make up a tub (plastic of course) of water with lime, baking soda and epsom salts in a high concentration and electrify a frame (steel mesh or something similar) with a 12 volt battery charger. Not sure what kind of gases this produces so I'll keep it all outside on the back porch.
From what I read, higher voltage will add the coating faster but at a reduced strength. With 4 volts getting a strength greater than that of standard concrete, I think I can afford to lose some strength for speed in my home aquarium. The higher concentration of minerals should also allow for a faster paced plating process.
The end result if all works well is custom rock quickly. No cure wait time as in concrete based rocks. To be sure about that, after the plating process, I'll put the rock in some saltwater and monitor the pH levels for a bit.
Any additional thoughts?