Phosfate media

[Oscar]

My algae issue was in pretty good shape until I added 2 clowns about 2 months ago (my first fish). Then the hair algae got out of control. I have done a lot of pruning and added Phosan in a media bag.

I am guessing that the extra phosphate came from the food. I am currently using: Hikari Marine-S Pellet Food and New Life Spectrum Small Fish Formula Pellet Food.

Is there any way of knowing with any certainty the phosphate level of a given food? Is it just a general assumption that all food has a certain level of phosphate?