I am currently doing an aquaponic project at school, in our school greenhouse. I have Tilapia as my fish. I have two grow beds, one on top of the other with the tomatoes on the top, a few peas on the bottom. Started in October of 2010.

:I planted cherry tomatoes

My tomatoes have been flowering for about a month now but still no fruit. Most of the flowers are dying. From other websites, I've read that I might have too much Nitrogen and that I need more Phosphorus and Potassium. How do I get rid of Nitrogen?

What should I do?