Dave m. pickly 2011-12-10 17:46:33
I just thought I’d toss this around the newsgroup and see what kind of
opinions I get: What does everyone think about adding more aeration at night
when the lights are off and plants have reversed their gas roles. I have
seen a few of my fish dwelling towards the water surface at night. I was
thinking about the possibility of adding a timed airstone for dark periods.
I am concerned about fluctuating PH, but more about oxygenation for my
larger bodied fish.
Thanx for any help you can give! 🙂
Troy bruder 2011-12-10 17:46:35
That’s exactly what I do.. Appears to work great!
Boris 2011-12-10 17:46:45
As matter of fact, I was just looking this up yesterday and found this
article… The following is an excerpt and below that is the entire link:
At night, on the other hand, the plants are actually using oxygen (and not
CO2) If there are not too many fish in the aquarium, then the oxygen
produced by the plants during the day will tide everyone over until the next
morning. However, if you notice that your fish are gasping at the surface in
the mornings, they are obviously running out of oxygen. To remedy this
problem, you can simply turn on an air stone when the lights go out. This
will keep up the oxygen level and remove excess CO2. I have the aquarium
lights and an air pump on two separate timers; when one turns on, the other
one turns off. It would also be fairly easy to rig up a solenoid valve for
the CO2 supply and have it turn the CO2 on and off with the same timer that
is regulating the lights.
Here’s the link:
Steve hampton 2011-12-10 17:47:08
It really depends on the setup. If you have a tank with high light
and fast growing plants and lots of pearling, then adding the
airstone at night could be counterproductive as it would probably
reduce O2 levels. It’s common for high performance tanks to carry
120% O2 saturation during the day. Adding the airstone would bubble
away both excess CO2 and O2. In lower light slower growing tanks,
especially those with high bio-loads, the addition on a nighttime
airstone may be unavoidable. Turning off CO2 injection at night
would be the preferred course of action, if fish were still gasping
then adding an airstone as a last resort.
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Gizmo 2011-12-10 17:47:49
I use aeration during the night.
I just started using a pressurized CO2 system one week ago which is already
The ph is steady at 6.8 and I also think it is very important to keep the
tank aerated when light are off in order to prevent big PH drops when plants
also eject CO2. It is also a factor depending on your fish stock and
Dave millman 2011-12-10 17:48:04
The “big pH drop” is exactly 0.2 in my tank. Measure it and see. Unless you have
a fish overstock, the aeration at night is unnecessary.
Dan drake 2011-12-10 17:48:14
This and a number of other postings seem to assume that adding CO2 pushes
out O2. This is not what they teach in chemistry classes (or, I think
thermodynamics classes). The dissolved gases don’t compete for space in
the water, but tend to reach levels that depend on the amount of each gas
in the air.
Adding CO2 could displace O2 if you opened up the tank and filled the
whole room with so much CO2 that you had a reduced level of O2; but you’re
not going to do this.
_Plants_ in the dark remove O2 and add CO2; but the removal of O2 is what
matters. Adding more CO2 from a tank won’t push out O2 unless you’re
bubbling so much through the water that it acts like a de-aerator. (And
even this won’t happen, according to the widely held opinion that aeration
does not work by exchange with the air in the bubbles, but by agitating
If there isn’t enough O2 in the water at night because the plants are
using too much, you’ll need to add aeration; this will increase the O2,
and it will remove some of the CO2 that you’re putting out money and
effort to pump in: not a desired effect, but an unfortunate side effect.
(I’m not saying whether or not it’s really necessary to do extra aeration
at night when you have plants. Anecdotal evidence says it is. Somebody
ought to do serious experimenting some day with a good O2 test kit. I
can’t, because my tank is massively aerated by the trickle filter, 24/7 —
and I use up a lot of CO2 that way, but it’s not all that expensive.)
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Chuck gadd 2011-12-10 17:48:32
Actually, plants respire (consume O2 and burn stored sugars) all the
time, day and night. It’s just that during the day, they produce more
O2 than they use.
Of all the CO2 injected planted tanks I’ve seen in person, none have
needed or have used aeration at night. And I’ve had and seen some
incredibly densely planted tanks.
Dave millman 2011-12-12 01:22:58
Chuck’s should be the final word on this.
Dave 2011-12-12 01:23:57
I have a PinPoint pH controller which turns on an airpump to increase
surface turbulence when the pH gets too low. I’m doing DIY CO2 with two
64oz juice bottles and a Hagen “Natural CO2 System” diffuser on a 29 gallon,
heavily planted tank. I’ve found that my pH drops by more than 0.2 at
night. The controller keeps the pH within a 0.2 range. If I were using CO2
from a tank, I’d probably just try to get the amount of CO2 injected to the
right level, but with the DIY CO2, it seems easier to inject a bit more CO2
than needed and let the controller level things out.
Dave m. pickly 2011-12-12 12:28:37
I don’t think I’ll worry about it. The fish that I’ve seen dwelling around
the surface of the water are not at all gasping for air…that’s probably
where they are most comfortable sleeping. Since I do use a “waterfall” type
filter I think the water turbulance is just fine for O2 support. And I do
realize that O2 and C02 are pretty independant of eachother. I’ll trust
your judgement on this Chuck since you seem to have enormous experience 🙂
Chuck gadd 2011-12-12 12:28:42
I notice many of my rainbows hanging near the surface at night. But,
my SAEs, which are known to be VERY sensitive to low O2 levels,
are sleeping on leaves at the very bottom of the tank. I agree that
it’s probably just where they like to sleep.
Clearly, if you see fish gasping at the surface, then fix the problem,
regardless of what any amount of experience says!