Sounds like hair algae. Don't put a phosphate pad in unless you are certain that you have phosphates. So test for phosphates and test for nitrates as they both are fertilizers for nusiance algae. Also, make sure that you are using RO or RO/DI water but test your water source also. Last, make sure you have good flow in your tank (powerheads). Certain fish, crabs, and snails will help keep the algae down as well.