the right care

Question
i have a one year old flower horn.Is 15 gallon tank just right for my fish.How should i know if my fish is a male or female(except about the anal pores).My fish is 7" long and 3" in width.

Answer
15 gallon is much too small for a flowerhorn. They need a 55 gallon all to themselves..possibly even longer.  I am not really familiar with flowerhorn fish and do not know how to sex them.  Your fish should be about a foot long by now if he/she is a year, most likely they are stunted from being in a tiny tank when they need a much larger one.