I have a 20 gallon tank. It's been up and running for about 3 months now. My diatom bloom has all but disappeared. My new thing is I've started to notice what I think is green hair algae in a few spots. I asked my LFS
for some advice on what I can do to get rid of it. They told me that I should check my phosphate level because if that is high, you will never get rid of the algae. I do 25% weekly water changes. My ammonia, nitrite, and nitrate levels are all at 0ppm. I haven't tested for phosphates yet. Is it possible for me to have a high phosphate level even though my water parameters are good and I do weekly water changes ?