| with the bio-load you have on that 15gal I would probably lean towards the reading on the Mardel strips. I believe Salifert makes really good test kits and would give them a try. In the meantime I would go to LFS and have them test your water and see what kind of results you get. I would also definitely increase the amount in the water change and do it weekly instead of bi-weekly. Although a fish only tank can handle the higher nitrate level they will definitely be stressed and could become susceptible to disease. You have to remember that with a small tank with a heavy bio-load your really have to monitor the water quality.
__________________ Robert
My Cube
“A spirit is manifest in the laws of the Universe—a spirit vastly superior to that of man, and one in the face of which we with our modest powers must feel humble.” Albert Einstein |