Well, phosphate is never something that you want, that is for sure. Phosphate can be fairly easily, over a period of time, be rid from your tank. Water changes (not tap water!!) and if you need to - a little kick of phosban or rowaphos. There is a million articles on each of these products, but basically both of them are good products. I assume you don't use tap water. Tap water is one of the sure-fire ways to INTRODUCE phosphates into your system for sure.
Any other reasons why you can't control the phosphate levels??