[lapoza]

Originally Posted by der_wille_zur_macht

hair algae on an algae reactor can reduce phosphate very quickly, but only to a point where it is limiting the algae's growth - it won't drop it below that point. For most people, that point is a healthy number, so it is OK.

The quickest method is probably LC dosing, but as others have mentioned, quick can be dangerous.

GFO is fine, too.

Many proponents of turf scrubbers will tell you to not use ANYTHING to reduce phosphate, as you'll be inhibiting the algae scrubber's growth and/or throwing nutrients out of balance. Algae scrubbers are great, but they can be finnicky in terms of interference with other nutrient control methods. Turf scrubbers target all the major nutrients but they need to be available in roughly the right proportions, if you're driving a single nutrient to zero (or close) through some other method, you'll ruin the performance of the scrubber.

That said, it is somewhat common for people to use (lower than normal) GFO or other phosphate control methods if phosphate is way out of control compared to other nutrients.

Which raises the question, what are your nitrate levels like?

The nitrates look to be between 0 and 5ppm