Scott,
I don't believe that is it in my case as I've been monitoring ammonia and nitrites and they are very good. Ammonia may get as high as .25 ppm and nitrites stay at 0 but sometimes go to 0.25 ppm.
It's probably a combination of the fine feed and the iron. I should have bought a separate filter to polish the water. I'm hoping I don't have bacterial gill issues as typically one uses flow through due to the high feeding rate and fine feed that is fed to fish of this size. I can't wait until I get them on floating and there won't be as much waste and mess!
Here are a couple pics of the smaller ones in the larger tank. They stay low until I start throwing in the feed and they they come up for it. Here some have come up and are feeding.
