# New to pressurized CO2, need help w/ pH crash



## Pan_Fry (Nov 14, 2007)

Hello,
I hooked up my first pressurized CO2 tank today (36 gal), with an Azoo regulator and magnetic valve. I don't use a reactor. I have one of those ceramic disc diffusers that sits underneath a U pipe I put on the end of my Fluval canister output. I also have an Aquaclear HOB filter that I run just as a backup (in case something happens to my Fluval.) Its set to low, but there is some surface agitation.

I also use a phosphate buffer to keep the pH of the tank around 7.0. If I use the pH/KH chart, will I get an accurate reading for hardness or will I get a bad number for CO2 ppm?

When I hooked up the CO2 system and ran it for a half hour (ok, I do admit it won't be heavily planted until tomorrow. There's a couple Vals, a sword plant, and two micro crypts). I just wanted to see how it ran. My angel fish and tetras started showing signs of stress. The bubble counter was about 3 bps with the valve pretty tight. I tested the pH with the standard blue reagent and got a 6.0 reading! I shut off the valves and degassed the tank.

Will the pH swings decrease with heavy planting (i.e uptake by the plants?) or do I need to really adjust the needle valve to put out less bubbles per second. I've had my angelfish for 4 years and don't want to lose him! 

Any input will be helpful here. Is it possible to raise the Co2 ppm that quickly without using a reactor? Should I stop using the buffer so I can get a more accurate KH reading and a better handle on whats going on with the CO2 levels?


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## Bert H (Mar 2, 2004)

First off, welcome to apc.



> I also use a phosphate buffer to keep the pH of the tank around 7.0. If I use the pH/KH chart, will I get an accurate reading for hardness or will I get a bad number for CO2 ppm?


You cannot accurately use the kh/pH chart with an added buffer. Why are you adding this? Let the CO2 be what drops your pH, not an external buffer. The best way to measure CO2 concentration is with a drop checker. One way to get an idea of 30 ppm CO2 is by taking a sample of your tap water and letting it sit out overnight to degas. Measure the pH. If you then drop the pH one whole unit, for example 7.7 to 6.7 you will be around 30ppm.

When going pressurized to start with, start slowly. I would do 1bps and see where you are overnight. If you then need to increase it, go to 1.5bps etc, until you attain your desired CO2 levels. But definitely lose the phosphate buffer.


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## hoppycalif (Apr 7, 2005)

If you have a Fluval 304 or bigger you don't need any more filtration, and if the Fluval has a problem, no disaster will occur. So, you don't need the HOB filter. You do need a small amount of surface disturbance, just a little ripple, to aid in picking up atmospheric oxygen, to help lower the ppm of CO2 at night, and to help avoid surface scum. A good way to get this is to have the filter output near the top of the tank, so the flowing water makes the surface barely ripple. I agree with Bert about starting slowly with CO2. Most tanks will need at least a bubble per second, assuming the bubbles are small, so start with that, wait a couple of hours or more and check the ppm of CO2. If you need more, and you do need at least 15 ppm, preferably 30 ppm, then raise the bubble rate a little bit, either by adjusting the needle valve or by raising the output pressure of the regulator. Don't ever increase the bubble rate, then walk away and leave it for several hours. Keep rechecking the ppm of CO2 every hour or so. Drop checkers are cheap, http://www.aquaticplantcentral.com/forumapc/sale-trade/38553-fs-co2-drop-checkers.html, for example, and they are the only way to be reasonably sure how much CO2 concentration you have, so get or make one and use it with 4 dKH distilled or DI water in it.


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## Pan_Fry (Nov 14, 2007)

Hi, thanks for the tips for monitoring a new C02 system! My Fluval is a 204. Does anyone advocate the practice of running CO2 through the canister, or is that asking for a mechanical failure?

One question re: buffers. My water is natually very very soft. I used the buffer to avoid pH swings that wouldn't necessary occur through the use of C02 (I used to use a yeast based non-pressurized system.) If I use the CO2 to drop the pH of the tank, would it be a good idea to fertilize for general hardness to make the plants happy, say using Equilibrium?


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## hoppycalif (Apr 7, 2005)

Many people run their pressurized CO2 system with tank water having 1-2 dKH, and some do it with even lower KH. The pH doesn't crash. Someone with a chemistry background posted here that about 5.5 pH is as low as CO2 can drive the pH. That is not going to harm the fish or the plants. GH is a totally different subject. GH is the measure of the ppm of calcium and magnesium (mostly) in the water. Those are plant nutrients, so you do need some GH for the plants. I think if your GH is at least 5 dGH, and your water quality report shows that there is some magnesium in the water, you have enough GH. However, it isn't harmful to add another 2 dGH to the water using Equilibrium, "Barr's GH Booster", or calcium sulfate and magnesium sulfate dosed at around 1 part magnesium to 3 parts calcium.

I haven't tried sending CO2 bubbles thru a Fluval filter, but I have read other's experiences here, where doing so can cause an "airlock" to develop and the filter stops pumping. It also can make the filter run noisily. In theory it can damage the pump rotor, but I don't recall anyone reporting an actual failure. Some other brands of filters seem to tolerate the CO2 bubbles with no problems.

A Fluval 204 seems to me to be too little for a 36 gallon tank, if you rely upon the filter to provide water circulation in the tank. If you add a powerhead to supplement the water circulation, the 204 is probably just fine.


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