black things

Question
My beta has a little black rectangular thing on the little clear fin by the gill and there's also a row of black along the bottom edge.  Please tell me what it is.  Thank you

Answer
Hello Linda-

The little black spots may be his natural coloration, but if they are raised up and look unnatural, it may be fin rot or an external parasite, like fish lice or flukes. The black edge sounds to me like fin rot: I would treat this by adding some aquarium salt to the tank and dosing with a medicine like QuickCure (from WalMart.) If the black spots are an external parasite, the addition of the aquarium salt alone should kill it off.

Hope this is helpful!
-Amber Worman