Not quite sure I understand the question but I'll give it a shot. And just so we are all on the same page.... a
diatom bloom usually is seen after a cycle. It's like a brown/rust fine coating on your substrate, your rock... everything. Sometimes when it's a bad bloom it can even look a little fuzzy. Very normal for this to happen. Some people try to "fix" the algae but if you just give it time it will go away. The bloom won't harm your fish but I wouldn't put corals in there until it was through. If some get on an exposed skeleton, or it covers the polyps, you may stress your new addition unnecessarily.
HTH
