What is your top off water Tds

[patpare]

I'm just curious how high do you let your top off water Tds go befor you change your RO/DI filters and resin?

My top off water is at 2.2ppm using a Hanna Tds pen.
I'm asking this because my phosphate are up to 0.09 and starting to get algae on some of my rocks and now I'm trying to pinpoint the source,I haven't changed anything other then my salt.
I only feed my fish omega one flakes every 2 days during the week and one cube of either frozen brine shrimp,mysis shrimp or cyclops.