Join Date: Oct 2010
Location: Victoria, Australia
I kept and bred B. channoides in the past, and never supplemented iron. They were healthy, constantly spawning, and produced living fry (although they didn't live for too long as the female would predate them).
I didn't even realise some breeders did this, until I did a quick Google search just now. I personally don't believe it's necessary to add iron. If it were, I think it would be mentioned much more frequently on wild betta oriented forums and FB groups.