Welcome to RAG!
Is this a new tank? It's not unusual for a new tank to go through a bloom of brown "algae". This is usually a diatom bloom and is nothing to worry about. It will go away.
If it's an established tank, all the advice about controlling nuisance algae applies. Check your water source, reduce nitrates and phosphates, check your carbon source (if used), check your lighting.
PS - It's not necessary to double post. I have merged the two threads.
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