Are you sure one of the other gouramies hasn't suddenly become more dominant than him? In particular, if that blue is a male, it'll eventualy become the dominant fish (at least over the pearl) and moonlights grow to 7" as well so that fish would be quite a bit bigger than the pearl in time. To be entirely honest with you, that tank has way too many gouramies in it. Mixing 3 trichogaster species and the 4 thick-lipped gouramies in only a 30 gallon may very well be asking for trouble (are they mature yet?). If they are all (or mostly) male, I guarantee you'll have problems... My second reaction was that your problem is due to stress from over-crowding. My first, and most probably the current problem, is that you have nitrItes over 0. In a mature tank, they shouldn't be detectable. You didn't say what your nitrAtes are but I suspect the problem is that you are not doing enough water changes to cope with the tank's bio-load. If the fish in the tank are full grown, you're actualy over-stocked at the moment and should do something about it if you want to avoid further complications. If you have a spare (at least 10 gallons), cycled isolation tank available, fill it up with clean de-chloarinated tap water (same temp. as main tank), add some plants and hiding places and then move the pearl in. I would expect the problem to resolve itself over the next couple of days afterwards. If not, the problem is probably bacterial. I'm only suggesting this because the environment he is in now may well be more stressful over-all than the move would be. Having said that, I'm assuming all the fish are mature (fully grown) and beginning to reachs exual maturity (and thus becoming more territorial and aggressive).