"Margolis" wrote in message
...
| nitrates are harmless. Don't worry about it. In fact in planted
tanks
| people try to get more nitrates

This is because the plants *consume* the nitrates, so while the
plants keep the nitrates low, this in no way suggests that nitrates
don't harm fish. My planted tank usually reads 0 nitrates, despite my
efforts to raise them with the use of fertilizers of various types,
and the fact that I rarely do water changes on it.
Nitrates are not harmless, it's a poison. Not as bad a poison as
ammonia, for example, but a poison just the same. Large amounts will
kill fish.