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Re: Oxygen injection

Ian wrote:
> The unfortunate by-product of this is that the surface area of a still surface
> is much lower than that of a highly agitated one, and therefore much less oxygen
> dissolves into the water and this can be harmful to fish.

In a tank set up for high plant growth (low agitation, CO2 injection), the O2
levels will typically be far above the O2 levels of a non-CO2 injected tank 
(no CO2, highly agitated). 

In a healthy and happy planted tank, the pearling that is common is because
the water is OVER 100% O2 saturation.   And even at night, the O2 level
stays at least as high as in the non-co2 tank.    And the daylight O2 level
in the planted tank was ALWAYS far above the non-planted O2 level.

These statements apply to my tank, and two other planted tanks that I tested.
I then compared the O2 levels to several non-planted tanks setup with 
lots of agitation.    I measured O2 levels about mid-day, and shortly before
the lights came on.    The O2 levels in the planted tanks were always higher
than the corrisponding O2 levels in the non-planted tanks.

I'm sure it would be possible to have a planted tank where O2 level could
fall dangerously low at night.   Very high fish load, poor plant growth,
high temps, etc could all effect the O2 levels.    

But, it's not a valid blanket statement that reducing all surface agitation 
will result in low O2 levels.  It can, in certain cases, result in higher 
O2 levels.

As for directly injecting O2, I'd strongly advise against it.   Just rig up
a reactor and inject air from an airpump.   Much easier, and same basic

Chuck Gadd