I have two geophagus surinamensis in a tank (450L) with 2 jewels, 1 convict, 2 rainbow fish, 1 pleco, 5 scissortails and 2 golden barbs. What's odd is the geos are skidding along the bottom on their sides. I've read somewhere that ammonia could be irritating their gills? Wouldn't that affect all the other fish? There is no redness to their gills. Could it just be something they do for fun. I also do about 20% w/c every 2 weeks or so. Any help?