# Help! Is CO2 slowly killing my fish?



## koffee (Aug 21, 2005)

As far as I can tell, my fish are healthy and happy. My RT Shark seems to be the most obvious indicator of things - he is deep black and brilliant red. And this is considering a major overhaul of the tank going of for the last month.

My 29 gallon has been evolving over the last few months, including a nearly complete tear down and rebuild a month ago to add sand. Most of the stuff that came out went back in, but I probably doubled the plants. I was using DIY CO2 then and still am now. Two 1.24 L bottles (2 C Water, 1 C Sugar, 1 tsp Yeast), bubble counter, standard (not silicone) tubing and check valve into the venturi on a 105 GPH power head.

At the peak, I can count a bubble every second or two and see a stream of various sized bubbles coming out of the power head. I try to avoid other surface disruption, but I run an internal power filter as well as a HOB. Outputs are below the water line, but cause surface ripples. The hood holds 4x20W NO (2 unknown, 2 6500K) and I want to up that to 4x24W NO 6500K as soon as I can.

As I said, my fish seem happy. Two dwarf sags, a val, and a anubias barteri v. nana survived the move, and a crypt melted. I now have 4 sags, 2 dwarf sags, a small val of some sort, a broad leafed sword, 2 anubias barteri (v. nana and coffeefolia), a cryptocoryne wendtii v. tropica, some ludwigia and some java fern. (Current photo below.)

I finally got a KH test kit today. It took me this long to learn that an alkalinity test measures that. According to the SeaTest kit, my German KH (tap and tank) is 9.1. Wow. My tap water pH is around 7.4. Double wow.

That's the min/max range of the test kits I have, so it is hard to be accurate. It could really be around 7.2 to 7.6 or so. According to a chart at the krib, that means my tap water has somewhere around 10-15 ppm CO2. At the very least, it is above the more average (?) 5 ppm. Does this mean my water would be good for a non-CO2 planted tank?

My pH test is a little more accurate in the middle of its range. (6.4 to 7.2 @ .2) A moment ago, I measured my tank again, and got 6.8. I could be wrong - it could be as high as 7.0. But even then, that works out to over the 20-24 ppm max that seems to be recommended for fish. Even if I fudge my readings a bit in the lower CO2 favor, I'm calculating 27 ppm. If I go with the exact numbers I think I got, then it is 43ppm.

How can it be this high with a somewhat inefficient DIY CO2 setup? How can it be this high without killing my fish?

Thanks


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## trenac (Jul 16, 2004)

Welcome to APC 

_If I'm not mistaken, I believe that the Sea-Test kits are for saltwater only. If so this is why you are not getting accurate readings. _

_The most important thing is to keep your water parameters stable when injecting C02. Keeping a KH of 3 or better and not letting your PH fluctuate up & down is the main thing. _

_Having a C02 reading of 27ppm is about where you need it. If it is 43ppm that is a little high, but not toxic to most fish; some fish are more sensitive then others to C02 injection. I've had my C02 levels much higher with no complications. _

_You may want to reduce the amount of C02 being injected into your tank to bring the levels down. You can also hook up an airstone or add surface agitation to release some C02 from the water. _

_One sure way to tell if your fish are being depleted of oxgen is if they are gasping at the water surface._


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## koffee (Aug 21, 2005)

The SeaTest kit is probably marketed as a SW alkalinity test. It was the only thing I could find at my LFS that might work. The instructions have a process for FW testing, and conversion formulaes to get various readings, including German KH.

I'm convinced though that my test kits are bad or too inaccurate, or something is in my water that ruins the standard pH/KH/CO2 calculations.

I'll probably keep messing around with them to see if I can get logical and understandable results. But I think my other "test" results are mixed.

My fish seem fine and happy... no gasping at the surface. So, that means CO2 is within there limits.

On the other hand, I haven't seen any signs of pearling. When might this happen? I would think that if I really were pumping in 47ppm CO2, I should see some of that.

As for pressurized... I wish. I only have two affordable options at least until next year. I can stick with DIY or I can remove CO2 entirely. Unfortunately, I'll probably have to go with the later.


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## trenac (Jul 16, 2004)

Most than likely your C02 reading is not 47ppm because of inaccurate readings of your test kits (PH/KH). This would be the reason for no pearling. I would get test kits made for freshwater, that way you will not have to make conversions in order to get your readings. Try ordering your test kits on-line since you cannot find any locally. 

If at all possible don't remove your DIY C02. If you do you will run into other problems, like dreaded algae from lack of plant growth.


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