i think if you don't get rid of the ugf you will always fight nitrates.. They are hard to keep clean. Too much sludge gets into the substrate which is difficult to keep clean with plants.. Many years ago I had a ugf and I could see from under the tank. I was able to put a thin, maybe 1/2", hose down the lift tubes and move it around to clean the junk from underneath. Had to do it often. I say, pull the tank apart, replant without the ugf.. Its a pain one time.. the ugf will be a pain for a long time..