I'm running 4x24 t5ho on my 26g bowfront. I'm wondering if this may be to much light for this size of a tank. This is just 1 reason I'm thinking that I can not get rid of my diatom issues?
Its not to much light, you are just in the last stage of cycling the new tank. This happens a lot when tanks are cycled under minimum lighting. Then you give it full light and it starts over, but this is normal with new tanks. I even git it when I let the bulbs go full term then change them all. I like to change 2 at a time.
Just hang in their it is hard but you are getting so close.