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Re: CO2

> I don't think that there is any difference between the two methods ONCE
> the CO2 is actually dissolved in the water.  The problem is simply that
> diffusors let gas escape out the tank before it is dissolved to begin
> with, while reactors trap the gas in a sealed chamber until it dissolves
> in the water.

CO2 is cheap, but you should not sacrifice circulation "ever" for keeping
more CO2 in your water. I think George Booth not long ago brought that one
up. The larger the tank, the more this issue applies. What works well in a
20 gallon or a 10 gallon will not do in a 125 or 150 gallon tank. Many folks
that switch from one to another sized tank have some issues with this.
If you like the disc, try another brand besides Ehiem also. Both methods
work well for our purposes.
> I guess what I was getting at was, in a large tank, say over 100 gallons,
> would good circulation be needed to carry the dissolved CO2 across the whole
> tank?

It will certainly help and I would have a good amount if it were my tank.
I'd rather error on too much CO2 lost to the air than too little
circulation. Slow to non circulated tanks are fine if you they are small(20
gallons or down-this is subjective) and have low fish loads or fish that
don't mind lower O2 levels.

> Here is my problem: In my 100 gallon aquarium I have had a real problem
> keeping a steady rate of CO2. I often get either too much, or too little. I
> have been using the Eheim, (is that spelled right?)diffusor. I have a fluval
> cannister spray bar set a couple of inches below the waterline. When the
> water evaporates to expose the spray bar, obviously I am burning off CO2,
> but when the water is full, I cant seem to reach the 20-30 ppm. I am either
> somewhere below ten, or high enough to start having sudden deaths of fish.
> On at least one occasion the CO2 tank was running near empty, and I suppose
> I could have had some dumping, but the main problem seems to be when I try
> to raise the CO2 level. I also had the diffusor at one end of the tank which
> gets very little circulation. The water surface would develop a milky film
> and a layer of bubbles, and then I start losing fish, mostly bottom
> dwellers. On Tom Barrs suggestion I moved the diffusor under the spray bar
> to throw the CO2 out into the water before it reaches the surface. It has
> appeared to help to some extent, but I am afraid to raise the CO2 level, and
> I am still at a level that is much too low.

Get good circulation going in your tank. It's okay if there's some surface
movement, then crank the CO2 in and see. Add a powerhead next to the out put
of your disc also so it blows all along the back of your tank. That will
> I have purchased a reactor and needle valve in the hope that the flow is
> more stable and easier to control, but I havnt had time to hook it up yet.
> To make things more difficult, I have a hard time with test kits because I
> am partially color blind.

Get a pinpoint etc pH monitor and you won't need to mess with color.
That will take care of that once and for all. And as much as most of the
folks are into plants here on this list I think most owe it to themselves to
get a decent method of pH monitoring.
Your KH will be more stable than the pH. Just ask a friend every once in
awhile to get around the KH. It's certainly is not as critical.

The needle valve will make precision attainable now. The reactor will be
more precise as well, responding quicker to your input of CO2. This can be a
bad thing if you add too much and forget to wait till it gets equaled out
and then go to work etc.
> I have taken a few steps: I clean the diffusor every couple of weeks, (a
> real pain) I shut off the cannister filter during water changes, and I keep
> the tank topped off with the spray bar pointed more down than out to prevent
> rapid CO2 depletion. The last major problem happended in less than 24 hours
> when I tryed to raise the CO2...when I got home from work I found several
> fish belly up and several others dancing in circles and banging their heads
> on the glass. I immediately changed 50% of the water and those that werent
> already gone were saved, and I then lowered the co2 again by one turn of the
> screw. The PSI is just under 15. (When I try and raise it, it jumps up to 20
> psi, which seems to be the level that is too much) Where it has stayed ever
> since.

Well it won't happen once the valve is added. You can lower your spray down
say 4-6 inches and slightly tilt it up to the surface to get a gentle
current across. That won't cause much CO2 loss and will help fish. It's not
illegal or something:)
FWIW I did lots of playing with circulation patterns. I still do. I love
that part of this hobby. I have a lot of circulation in my tanks. I have a
small amount of surface movement but large amounts of flow in the water
column and tend to have it coming off the bottom back edge of the tank in
larger tanks.
> Am I correct that a reactor would solve my problem?

I think it will make a precise level much easier for most folks to attain.
As far as a cure all, no.

> Oh BTW, Tom tested my KH for me and said it was around 5 if I remember
> correctly. Is that right Tom?

Yep, dial in a pH of 6.8 to 7.0 on a pH monitor.
Adjust with a nice needle valve. I think you'll be amazed once you've tried
this out. It'll be like "What was I thinking!". Copy a pH/KH/CO2 chart down
and place it next to your pH monitor.

CO2 is too important not to check and deal with in a decent manner. Most
folks can trace their issues with planted tanks to CO2.

Another thing is adding a pump to a reactor set etc and turning it "off" or
"on" moves and **circulatates** the water more than the disc can ever do and
they can do it when the the CO2 is "on". This helps move the CO2 to the
plants. Chew on that for awhile and consider how it might help a plant tank
out more than the "other" method. Also, where does the disc add the CO2? up
towards the surface rather than down at the bottom or where ever you wish
using a pump driven reactor. What if you have a shallow tank? I think they
(disc) are good for smaller tanks. But so is adding the CO2 to the filter
intake if you have a small tank...
Tom Barr