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Re: [APD] aeration & a planted tank

Oh yes. I missunderstood you. I thought you meant it
pearled for days and I assumed this meant most of the time.
If pearling is easily accomplished, I suspect that O2
levels are relatively high. With pearling in the daytime
and morning-gasping, the O2 swing is pretty intense. I
guess that was my point, albeit irrelevent.

Just to clear my brain slightly -- 

The CO2 is higher at night (if you run CO2 24-7).
This is inconsequential -- the pH swing is usually on 0.2,
maybe 0.3 units. If one feels one must, one can perhaps
avoid the variations by using a solenoid and pH controller
(within the the trip range of the controller (although
controllers often have trip ranges about 0.1 or 0.2 units).
Swings might be a little larger if running CO2 on solenoid
with a timer set for daytime only.

Adding CO2 will generally yield elevated O2 levels, even
during darkness when plants are net consumers of O2.

The O2 is lower at night when plants are net consumers of
O2 along with the fish and aerobic bacteria. The question
of the day (or last few days) is how much lower. In the
past I  haven't heard of many measurements other than the
broad measurement of gasping/not-gasping. And I am curious
under what conditions the morning-gasping occurs --
certainly (uh, apparently) not all densely planted tanks
without CO2 added. Is water circulation enough? Is
agitation necesary? 

I will toss in here that, if I wanted to add gas to the
water because of a chronic morning-gasping conditon, then
before adding a water agitator (airstone), I think I'd
rather just add CO2 at least in the daytime to get higher
O2 levels. Of course the start up costs are a lot higher
for adding CO2 wuith compressed gas than for an airpump or
venturi powerhead -- otoh, a fermetaition bottle is cheap
than a pump.

I've used biowheels in the past so yes, I have used
aerators of a sort) but that's only bacause I have a
boatload of them and occassionally using one convinces me
not to throw them out. Of course, this doesn't explain the
rest of the ton of equipment in the basement I'm not using
at the moment. Actually I have use them to see how they
perform, leaving aside compressed-gas CO2 equipment to do

Can more folks report on non-co2 set-ups where they don't
have morning-gasping and don't have aeration other than a
water (or filter) pump?

Scott H.
--- "Terry S." <tgs1 at rni_net> wrote:

> > Pearling is a sign of O2 saturation.
> Yes, it is.  And your point is?  :-)
> I guess I wasn't clear - the pearling occurs in the
> evening.  In the
> morning, when the O2 is low, there's no pearling.  Only
> fish 'gasping' at
> the surface.  It would appear to me that the oxygen is
> being depleted at
> night by the rapid plant growth.  No?
> Terry in AZ
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