I agree with Zooz. When brown algae disappears like this, it means that there is enough bacteria in your tank to kill it off (a good thing). This also means that you are usually nearing the end of a cycle.
I also agree about the clownfish. There is a chance that they will get quite agressive towards each other for a bit, until the female becomes the complete dominant, almost, and they learn to live with each other. She is showing up the measly little boy, that's all.
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