See, I've been a city girl my whole life, so I have no idea what crushed oyster shells have to do with poultry.
My aquarium is a small tank. I don't keep cichlids, though I would like to at some point, when I have time to maintain a larger system. The one I have currently is 10 gallons, freshwater and stocked with cardinal and ember tetras, a truck load of cherry shrimp and a bunch of anubias. The only concern for me, is that I do have one orchid that I just switched to using distilled water on because it wasn't thriving as much as it should be when I was giving it tap and my tank uses tap water treated with prime.