Do not use any more algaecide. No algaecide is completely compatible with chlorine; even polyquat, though it's more compatible than most.

The ultimate results of using anyone's phosphate remover will be the same, but apparently the Kem-Tek product I linked costs 1/2 to 1/3, per unit phosphate removed, of what the Pool Perfect products cost. Keep in mind that neither borax nor phosphate removal is a solution; both simply make it harder for black algae to recover from damage done by chlorine.

If you can post the EXACT model and make of your filter, I can possibly help you find a higher quality replacement cartridge that will do away with the need for a DE filter.