I have 2 convicts in one tank and one of them has this reddish dusty
rust
colour to his sides... Now he has had it for quite a while and I was
wondering if this is anything I should be worried about?

Thanks.


Female convicts have this red coloring on the sides.


Yes that is the female. They do that when ready to breed. And keeps a rosy
belly to help the fry identify her. If she has fry leave her with them, as
she is a very good parent. The male will also guard the fry and is very
aggressive when with fry. Mine had about 20 fry survive and doing well.
Give them a hidden rocky area and they will be happy.