Assume you mean .05 phosphate. Salifert makes good test kits. I use Hanna for PO4, Alk and Calcium. Tropic Marine pro for nitrate. Salifert then for Mag. If the hair algae is fragile it could be starving which is good. However, it’s all natural just unsightly. CUC will keep it at bay as long as you stay on top of maintenance