You need to test your water, its likely a phosphate issue as stated. You need to check the TDS
of the water coming out of your RODI
, if you are putting phosphates in when you make up new water no amount of water changes will get rid of it. So get yourself a phosphate test kit or meter, a TDS
meter and figure out the water problem.
To get rid of the hair algae, you can pull it off with your fingers or hope the snails and tangs eat it. Ultimately you need to starve it and thats why having perfect water is so important.