you need to rinse any decor you place in the tank. there are lot's of options here. You could silicone slate together to form a cave. You could put alot of colored quartz on a piece of slate to make a cave. Another thing that i've never tried but have wondered how it would look is to take a piece of tupperwear cut some holes in it smooth the edges and silicone sand/gravel all over the outside of the tupperwear. you can also use coconut shells but i don't know how to treat them... Or you could take a look at the links in my signature. I can make custom pieces too. Oh one more thing you might try is a terra cotta flower pot. With any ornament make sure that any holes are either too small for a fish to fit it's head into or large enough for all of it to fit through. Also make sure you remove any sharp edges from slate/crystals/tupperwear...etc. Hope that helps.
