There are other factors in water that mitigate the fluctuation in ph, so it
will vary from person to person. I'm sure the amount of CO2 you inject also
makes a difference. Pressurized systems are setup to go off at night,
partially to save CO2 when it's not needed, but also for the ph fluctuation.
It's been a long time since I tested the fluctuation in my tank with 24 hr
CO2, so I don't remember the numbers, but it was at least one, which I've
read can be stressful on sensitive fish. Matt, if you don't want to bother
with turning the CO2 off and on if you don't have to, just test the ph right
before the light goes out at night and right before it comes on in the
morning to see what the difference is.

Also, I question the idea of adding aeration. As Dave mentions, oxygenation
of the water drives off the CO2, so keep your powerheads from agitating the
surface as much as possible, and only aerate with airstones if you are
adding medication or if the fish are all at the top gulping for air. It's
amazing how much oxygen the plants inject into the tank water.


"Dave M. Picklyk" wrote in message
news:QSo3d.26824$yW6.15464@clgrps12...
I've tested and noticed only 1/10th change in pH from day to night. That
slight fluctuation shouldn't harm fish at all. A common myth is that the
more CO2 you have saturated in your water the less O2 you have. These
values
are ALWAYS independent. As long as you have proper aeration such as an
airstone, waterfall/powerhead which is generating oxygen I wouldn't worry
about it at all. Just make sure your surface turbulance doesn't dissipate
the CO2 that much.

Dave.


"Allyb" wrote in message
...
I don't know what happened to your fish, I think bucky may have been
right
about them sleeping. Do you normally check them after the lights have
been
out a while.

Actually I was writing to mention something about CO2 and ph swings. If
you
leave the CO2 going with the lights out when the plants can't use it you
can
cause dramatic ph swings which can be really hard on your fish. I
solved
this in my diy system by routing my CO2 through a gang valve. When the
lights go out I just open one of the vacant valves, and the CO2 vents
into
the room instead of into the tank. Before I go to work in the morning I
close the valve. Make sure you use check valves if you try this so you
don't let a lot of oxygen into your CO2 engine, or siphon all the water
out
of your tank :-) Good Luck!


"Matt C." wrote in message
...
HI all- Newbie to this group here

I have a 29 gallon freshwater tank and i just spent about 2 1/2
weeks
planting the tank. I installed a 1 liter DIY CO2 system yesterday and I
noticed last night at about 11pm, that it was bubbling nicely through a
microfine airstone located at the bottom of the tank. By this time
(11pm)
the tank light had been out for about 2 hours, and I popped it on for a
few
minutes to check on the fish and they were all very palecolorless and
hanging out on the bottom near the CO2 airstone.
The fish are neons, glo-lights and pristella Tetras and two dwarf
gouramis. All were very subdued. If they werent getting enough O2,
wouldnt
they be gasping at the surface? I dont know if this is from the co2 or
not,
but I unhooked it, cranked up a regular airstone and put them to bed.
This morning they are all happy and fine with good color and swimming
around
nicely.
Anyone have a thought on what I saw last night?
Thanx!

--
Matt C.
http://home.comcast.net/~briarbushbrewery/