Cool project. I'm very interested to see ow it progresses.
I have two 6 gallon tanks running. they do really well with minimal algae, and minimal water changes, BUT the key to these tanks is aptasia

. One is my nudi rearing tank, and the other is my aptasia rearing tank. I don't have any corals in them, other than some blue cloves. Thr rock is full of pods and brittle stars. I feed the tanks quite heavily with all flake food I have left over, it's either crumbled to dust or the fish just wont eat it. It's amazing how aptasia really do filter the water.. Too bad they are such a pest!
I know which man made rock your planning on using and also know its been curing for ages..BUT I'm wondering if it ever really stops off gassing? In a tiny tank like that it will become apparent quickly if it is still leaching. I did a background in a 20 once, and even after 2 years it was an algae magnet.
Keep us informed and lot of pics please!
