High phosphates-using reactor and can't get them down

[gregzz4]

Originally Posted by LeanneP

Should I only be using 100 mls at a time?

It sounds like you do have quite a heavy PO4 issue so use whatever you need to.

Originally Posted by intarsiabox

How is your nutrient export?

I think you've hit it on the head.
Without consistent rock and sand cleaning I guess her PO4 is built up and now releasing.