Nitrogen: 5ppm nitrate and <0.05 ppm ammonia Phosphorus: mineralized phosphate 0.1 ppm (I defer to Tom) organic phosphate << 0.01 Potassium: 10-40 ppm (in mineral form, is there any other kind?)
Personally, I haven't yet had the guts to add phosphate to my tanks except in clay ball form. I typically use soil with peat as a substrate and amend it with clay fertilizer balls.
I'm not convinced at all that increasing nitrate & phosphate in the water do not cause algae to grow faster. In other words, I believe that if you increase them in the water you will stimulate algae growth.
-- Andrew McLeod thefish at theabyssalplain_freeserve.co.uk