I set up a tropical 20 gallon tank 6 weeks ago and cycled it with a yabby, after which i added a dwarf gourami, baby red tailed shark, and two guppys. The yabby does not threaten the fish at all. Ammonia nitrite and nitrate are negligible and have been since the end of the cycle. Recently my gourami has red sores, one on his lower jaw which went away, then one which grew on his forehead to quite a size, and a smaller one on his side. What are these sores and how should I treat them?? in addition, the colour of the shark is highly variable, and he is very timid and hides most of the time. All fish are visibly eating, except the red tail shark who can be seen picking from the bottom but never comes out at feeding time. The tank is quite well planted, with lots of hornwort and a val plant in the corner. Is the shark's behaviour normal, and what should I do about the gourami?? Any help would be greatly appreciated
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