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Re: O2 round two

Michael Eckhardt wrote:
"'Optimum Aquarium' (Dupla) provided a graph in one of his subsequent books
that showed the O2 level in one tank with and without a trickle filter"

This was pretty much the answer I was looking for in my second question.
Thanks Michael!

Roger Miller wrote:
"my reading suggests that oxygen stress sets in for many
warm-water fish at about 4.5 mg/l."

Ouch! I will take a close look at my fish when the light comes on. I don't
think I've seen oxygen stress in the mornings. Anyway it seems that the
tester or the test generates faulty readings =).

Chuck Huffine wrote:
"At night, just before lights
out, levels were greater than 10mg/L, which was the limit of the test's
scale.  Saturation (i.e., pearling) was reached around an hour or so of
lights on, so I'd imagine that levels just before lights out (10hrs later)
were probably well into the teens."

It's getting more and more obvious I have some strange readings..

Bill Wichers wrote:
"2 mg/L seems *very* low. I would expect some fish deaths at that level. If
you're having problems with O2 levels getting too low during the night, you
should probably put in an airstone on a timer to start running at some
point after your lights go out at night, and stop running at some point
after your lights come on in the morning."

Regarding the fish see my response to Roger Miller.
Actually I now have a pump with air-venturi going all night and I'm really
thinking of combining it with extra airstones.
I will also lower the temperature from 28-29 to 25-26.

New question:

I have a Fluval 404 with good throughput in my 310 litres tank, which
I thought would be more than enough to aerate my tank. But I have
a slim-tight light-hood packed with fluorescents that covers the whole
aquarium - could this be the reason why  the oxygen levels drops so
much when the lights go off?

// Daniel.