What causes increased phosphate levels in aquariums?

Question

My tropical fish tank has high levels of Nitrate and Phosphate. I did a 50% water change to deal with the nitrate levels but how do you deal with phosphates?

Answer 1

Assuming there is no/low level(s) of phosphate in your water source, water changes will do the same as it would for nitrate.  Phosphates build up as left over food accumulates, so frequent gravel vacuumings are a good preventative measure.  Phosphate isn't dangerous to fish, but it will, in conjunction with nitrate and light, lead to algae growth.