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[APD] Too many plants??

Kevin wrote:
> <snip>, Too many plants?
> Every day, right before my lights turn on, my fish
> are breathing heavy and gasping at the surface of
> the tank. After the lights are on for a while,
> they seem to go back to normal.
> This to me sounds like too much CO2. <snip>
> I've also been pumping Oxygen into the tank 24-hours
> a day for the last 3 days.
> So what the heck is going on? <snip>, lots of
> <27 fish, pH 7.2, Nitrate 0, 40% water changes/week>
> <snip>

Hmmm.  That *is* a puzzler.  It looks to me like
you're doing everything right.

Of course, we *know* what's going on:  It's not
enough oxygen (fish gasping in the morning, fine
after the lights are on).  Things could be complicated
a little because of some kind of system toxicity
(I agree with Rushui that high Nitrite levels will
poison fish, and they will have trouble getting
oxygen).  But, at 40% water changes a week and no
fertilizing, ...

Your fish load isn't that heavy for a 70g, but the
plants *do* displace water (as well as your rock,
etc.)  I'm curious as to how many gallons you really
have.  Plant respiration at night is significant,
so even though you're actively bubbling oxygen...
I assume that's just an air pump?  It simply may
not be able to keep up.  Do you have a lot of current
in your tank?  That will help quite a bit.

I suppose it's possible that your plants themselves
are producing toxins or other compounds that cause
some sort of toxic reaction in the fish, or help
inhibit oxygen uptake.  But, the fish are fine
after the lights are on for a bit.  So, it seems
like it's *got* to be the 'lack of oxygen' thing.
Is your tank warm?  (I didn't see the temp in your
stats.)  Dissolved oxygen drops considerably as your
tank heats up, and you have 200 Watts of light.

It's got to be the oxygen.  Maybe throw in a couple
powerheads that run at night, drop the temp, and
make sure your air pump is a big one.  Worst case,
you can drop your fish load... 23 fish in a 70g
should be fine, but if they're big and you effectively
have relatively little water (because the packed
tank displaced it), then you might look at your
tank as more like a 40g (and 23 fish x 2" each is
too much).

When I was a kid I cought 50 minnows and threw them
in a tank, so packed full of lake grass and cobomba
that the fish didn't have a lot of room to move
around.  After setting it in the shade, two hours
later all the fish were dead.  The temperature was
fine, but I think they died of lack of oxygen.  I
felt so guilty...

After all, fish are people too.  ;-)))


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