I have two dwarf gourami and 4 tiger barb is a 120 litre tank. I know the barbs and gourami are not ideally suited, however the barbs being half the size of the gourami have showed no sign of aggression toward them and any squabbling has been kept between their own kind. The two gourami have shown a similar story, with each claiming their own half of the tank. I did a 10% water change yesterday and all was fine. Today I notice what looks like a trace of white fungus on the end of the fins of one of the gourami. Without being 100% certain of what it is, I do not know the best wat to treat it. Any suggestion, please? The fish otherwise is behaving normally. I could transfer him into another tank with two thick lipped gourami but am concerned that any transfer I do is likely to spread the infection to another tank.