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"NetMax" wrote in message
.. .

"Jim Morcombe" wrote in message
...
Comments invited. Do I have this right?

I am "often" forced to have too many fish in a tank for a while.

When you add a heap of fish, the ammonia level increases. Most fish
are
quite tolerant of high levels of amonia, while others drop dead
quickly.

Once comment: if you keep the pH below 7.2 or so, almost all
the ammonia is present as ammonium (the NH4+ ion of ammonia) instead
of as "real" ammonia (NH3). Ammonium is much less toxic than ammonia.
But, of course, once the ammonium (or ammonia) get converted to nitrite,
the fish will die of the nitrite spike...

Beware that NO3 is a 'silent' killer. Fish exposed to
water shock of greater than 40ppm NO3 will exhibit varying degrees of
discomfort, and the smaller the fish, the more likely the shock will be
fatal, either directly, or indirectly through Ich or some other disease.
Nitrate shock is what kills new arrivals (when the rest of your fish are
fine). IME, death occurs on or before the 3rd day.


Interesting -- I didn't know that. Might help to explain why I had the
odd inexplicable death among new arrivals. (My tank was at zero nitrates
for quite a while before I wised up and started dosing nitrates -- I
now keep nitrates at around 10-15ppm.) I suspect that 40ppm or more
wouldn't be unusual in many fish shops. I think I'll test the water I bring
the fish home in next time. Might learn something new that way.

Now, here is the real question: say I just bought a bunch of fish
and they are swimming in 60ppm nitrate. Now, how do I get those
into my 10ppm tank without killing them? I normally acclimatise
new arrivals over about an hour, gradually adding small amounts
of tank water to the bag and then transfer the fish. But I suspect
that an hour is too short to overcome a 50ppm change in nitrates...

Cheers,

Michi.