Two things: one - calling Soares is definitely worth a buck or two. Two - - under ground/gravel filters. My thought is that if you really want a sewer in your tank, go for it. I have to admit I tried them but do not like them. I have had baby fish trapped by them years ago. My fish dug through the gravel. Stay away from under gravel. Use some sort of sponges, even in big tanks if you like. What's the rest of us think on this one? Happy Halloween (just a bit early). Anybody hear of Apisto Cruzi. My local store was selling them and I have not seen or heard of them. Not in Linke and Staeck's Dwarf Cichlids. No Scotch and I'm still rambling. Bye.