thanks . . . I'll give params later tonite, let you know if anything is out of line . . . last checked this weekend, was 0-ammonia, 0-nitrite, <5 nitrate . . . it is a heavily planted tank, so I typically dose nitrates, they are next to none otherwise . . . the water is medium-soft, neutral Ph . . .
I do water changes every week, about 15-20% on average . . . do not do a heavy gravel vac, because I don't want to disturb the plant beds . . . i've maintained this routine for several years, but this is the first sign of a problem
thanks for feedback . . .