If your refering to the rusty patches that's diatoms you get these in a new set up and it comes and go's again so don't panic if your whole tank go's brown. It's normal. Hair algae however is a different story it can quickly take over a tank and is horrible to get rid of,remove it by hand and try to be carefull that loose bits don't blow around as I can bed in again and quickly spread. Hope this helps