Hi. I have a 120 gallon tank that has an automatic drain/refill situation - a little every day. My tank is lightly populated with cichlids, because they share their habitat with a red eared slider. I have some hornwort. But no other plants (or snails) and a few plastic decorations. One of my cichlids (a yellow one, but I dont recall the species) has developed some browning on body and tail. Otherwise the fishie seems fine. Eating and swimming well. No apparent damage other than discoloration. Any ideas what this might be? I haven't run across it before. I feed a variety of lettuces, dried crickets & worms, cichlid pellets and flake food on a rotating basis and occasionally add feeder minnows.