I had my tank for Almost a year now & my phosphate always been 2.0 I been trying to get it lower but I can't ..I don't use tap water for my water change I just did a 10G water change yesterday & nothing changes .. I have a 56 G
test you water you are mixing. test your test against a fellow reefers test or at lfs. if these give the same readings then gfo in a reactor/ I like rowaphos. you can also dose vodka but do the gfo first for a while and see where you are at. also add some macro algae to your system.
You need to tell us more. One are you using RO/DI water. If so what are your TDS reading. Should read 0.How many times you feed your fish. Do you rinse your food if its frozen food. What kind of system you running. Are you using if any? GFO Ect. How offen do you do water changes. What brand of Test kits. Phosphate are entered from over feeding. Also Water that's not filter from Ro/DI. Bad membrane or bad DI can cause phosphate to enter. So you need TDS meter to test your water before your introducing it to your tank. You work from there first.
On the food it's more frozen / I'm running Refugin / don't know the Ro/Di water but I buy my fresh water at a pet store / my reactor just came in & don't know which one to buy for GFO / & I don't own TDS METER yet /
You need to test the water your buying. Very possible it's coming from there. Did you test a fresh batch of new salt mix. Say make 5 or 10 gal freshly made salt. Test your phosphate in the new mix. See if its coming from there. Its good to rinse frozen food. . But only way to find out is testing your water. Reactor will quickly remove phosphate. But you want to find out where it's coming from. I say it's very possible it's coming from your water your buying. So if you don't have RO/DI and TDS meter. Do what I said. And other thing are you using same water for top off. If that water has some phosphate. Once again your introducing more phosphate to your tank. Every time you add water. Work from there and let's see.