30ppm CO2 (rusty brain)
 

Hi

I've had a planted tank before, with pressurized CO2. I've had a year and a half break from aquariums, and now moved to a new city.

I've measured the tap water here to be pH 7 and KH 11. From the pH/KH/CO2 relationship tables, it would appear that my tap water already contains around 30ppm CO2.

Am I correct in thinking this? (My brain feels a little rusty on these matters)

If this is correct, I guess I won't need to buy a CO2 injection kit for the new aquarium I'm going to be setting up?

Thanks

It certainly does not contain 30ppm of CO2. There are other things in the water that can alter the pH or KH. That's why I really don't understand how these pH/KH/CO2 tables are supposed to be of any use.

Thank you for your reply. If that is correct how would someone with my water parameters be able to dose CO2 without dropping the pH dangerously low?

Thanks

Co2 related ph swings have no effect on livestock

You can let a small sample of water rest overnight in a wide pan, or shake it vigorously in a bottle with a lot of air, to drive off CO2. Then retest pH.

If it rises a lot, I suppose it's possible that your tapwater really has 30ppm CO2. But a 50% water change will only raise your tank from 0ppm to 15ppm, and then only for a few hours. So you'll still need CO2 injection.

Otherwise, you'll need to do some more investigation into the cause of your odd readings.

I agree that using tank water is no way to measure the CO2, but a drop checker would be more accurate and fairly useful in a planted tank when dosing CO2. Since it uses a 4 dKH solution with typically just baking soda, then it's more accurate than testing the pH of the tank water since there's a lot more going on in there. However, I wouldn't consider it to being close to exact, but it's still a good indicator of the dissolved CO2.

Thank you everyone for your replies. So if I am correctly understanding what has been said, my tap water's readings of pH 7 and KH 10 do *not* mean I already have 30 ppm CO2.

If I inject CO2 into water with these parameters, won't my pH drop?

Also, if I can't use the pH/KH/CO2 tables to calculate CO2 ppm, how would I go about determining this?

The drop in pH caused by CO2 dosing shouldn't have any harmful effects on the fish. And like I said in my previous post, the only somewhat accurate way that the typical hobbyist can measure CO2 is by using a drop checker with 4dKH solution.

+1. A drop checker is the cheapest and most convenient method of measuring ("estimating") the CO2 level in your aquarium.

There are more expensive options, but these are usually outside the price range of the hobbyist.