intotherain

I'm making my 340L tank soon with CO2 and 216W T5,
the tank will house rare plecos and shrimps... both in need of lot of oxygen..
the tank will be planted but I'm not sure it will be enough O2 production...
I was thinking on adding an air pump to the tank just to be sure' I will run it 24/7
but will it take CO2 out?

thanks.

searley

i dont think the addition of bubbles/o2 will take out the oxygen

most co2 / o2 exchange happens at the water surface, suface movment causes the co2 to be expelled

hence most articled on setting up co2 advise adjusting spray bars so there in minimal surface movment

i guess if you are not causing excessive surface movment you could increase the co2 input to make up for it?

Zapins

I don't think you will need additional O2 in the water. Just don't put the Co2 up very high and you should have no problems at all.

It is only when you really gun the CO2 (5+ bubbles per second) then you start to see fish breathing fast and gasping.

I have kept shrimp in my CO2 tanks for many years and they have never had problems with breathing, neither have the fish.

Lots of CO2 will not displace O2 from the water. Though adding a bubbler will certainly displace CO2 from the water. In a sense it would be counter productive to add a bubbler 24/7 since the CO2 you add would mostly be degassed before being used and the overall CO2 level would remain close to ambient.

John N.

Good info all above. I agree that adding an air pump will release the CO2 due to surface water and atmospheric exchange (more water contact with the air).

If you are worried about CO2 levels being too high, you can always run the CO2 on a timer, on during the day, and off at night. Also you can place an air pump on a timer, to run at night to increase oxygen exchange there.

-John N.

intotherain

I will have my CO2 on a timer, I heared that if you put and airstone at night when the CO2 is off then you will experience PH shifts very fast and that real bad for fish...

is that true?

John N.

Somewhat true. You do get a pH swing between 0.5-1.0 when you turn the CO2 off at night. However, I've done this for months, and never had any fish deaths yet. The pH swing isn't that detrimental to fish since this is sort of what happens in nature.

Another way you can think of it, if you leave your CO2 on, you also are causing a slight pH drop throughout the night. Plants will respire CO2 at night adding to the current tank's CO2 injection count, and dropping pH futher. So you are getting a swing either way if you decide to do 24/7 or daytime only.

Again, best thing to do if the concern is great C)2 during the daytime, and airstone at night (even timing it where the airstone goes on in the middle of the night for 2-3 hours, will help minimize whatever swing there is, and oxygenate the water).

However, I wouldn't worry much about the pH swing. I don't fish and shrimp have been happy.

-John N.

intotherain

thanks john!

NE

As i have understand it, the main thing fish fell bad about is changes in osmotic pressure, and that is not affected due to co2 but with most other ph changing things.
So changing pH due to co2 will not affect fish that much.

Salt

My own testing has shown that if you have a good amount of flow to the tank, an airstone will outgas some CO2, but not all. In my case, I lost about 3 to 5 ppm. Turning the CO2 up slightly compensated.