co2 bubble rate

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Registered Member
Jan 25, 2002
The Big D
i need some serious help with getting my pressurized co2 system worked out. i have the bottle, a regulator, needle valve, and bubble counter. for now, no funds for a reactor so the co2 goes into a magnum 350 and then into the tank.

first, specs and then my problem.
30 gallon tank.
110watts CF lights @ 6700K
3" or so of flourite
ph always around 6.8
no ammo or nitrites, barely discernable nitrates
i don't remember anything like kh, gh, ... and now my test kits are out of date
a few baby loaches, a bunch of tetras (lemon and serpae), some flag fish, two danios, juvie gold nugget pleco, and a partridge in a pear tree:)

lots of plants, don't ask me what, i don't know. crypts, vals, anacharis, and about 5 others that i don't remember the name of.

had pretty good results with using yeast until it got to be too much of a PITA to keep up with.

so i get my pressurized co2. going with three or four bubbles per second, i almost lost every single fish. i came home from work and the were all at the surface and the gold nugget was upside down on the bottom. yeeouch, co2 off immediately and a big water change and happily all fish recovered. obviously i used too much co2. what should i be shooting for here? also, what fertilzers should i be adding? flourish? excel? thanks in advance.


2009 VMAX
Jul 6, 2002
You need to test your PH and KH. And, then go and look it up on this chart.


Fish?.......What Fish?
Aug 19, 2002
Somerdale, New Jersey USA
The bubble rate depends on how much CO2ppm you want in your tank. I'm a DIY guy, but if I was in your position(lucky you), I'd start with 1 bubble every 2-4 seconds and test pH and compare to the kH/pH chart for ppm. You want to keep it at 25-30ppm. You can work from there. You are really going to need atleast a new pH,kH and Nitrates test kits because until you get a handle on the requirements of your tank those parameters will need close observation.
Then click on Search in the upper right part of the page and type in "nutrients" or "fertilizers", and read every thread written by Plantbrain(Tom Barr). He keeps it simple and his dosages work for many of us(definately for me).
BTW, it's MUCH cheaper to get the nutrients you need in bulk rather than using SeaChem products although they are good. You are running almost 4/1 watts per gallon and your nutrient needs will be high.
Hope this has helped.


AC Members
Apr 27, 2001
Davis, CA
Bubble counts are only a rough measurement.
pH/Kh is need to determine the pH you will need to hit a target CO2 level.

You'll need perhaps a bubble every two seconds at most for a rough guessimate. You likely had 50-100ppm in your tank at 3-4b/sec.

That's(3 to 4b/sec) about right for a 125 gal tank.
Once you measure the KH go down and read down till you find the pH ranges to get a CO2 in the 20-30ppm range.
Add enough CO2 till you get the pH in that range during the daylight period and keep it there by adjusting the needle valve.
That's all there is to it. You just watch the pH primarily. Check the KH every so often though in case the utility company changes their sources, rain/snow melt etc in the spring....etc. Generally the Kh is pretty stable. Shoot for KH of 3 or over.

Tom Barr