New to CO2 - The Planted Tank Forum
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post #1 of 4 (permalink) Old 11-23-2008, 06:05 PM Thread Starter
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New to CO2

Hi, I just installed a pressurized CO2 unit Wednesday. This is a 178 gallon heavily planted tank using the Rena XP3 as a CO2 reactor with the CO2 tubing inserted into the intake of the canister filter. The PH of my aged tap water is 7.8 so I set the PH controller to 6.8 the first day after calibrating the probe. After a few hours the PH dropped to 6.6-6.5 for a couple of days.

Yesterday I decided to run some tests.

I have a CO2 test kit. Yesterday it took 26 drops to change the color (26 X 2 = 52 ppm CO2)...then the kit mentioned hard water would test higher than the 10 -15 ppms that you want to keep it at. Basically that told me nothing.

PH 7.8-8 (aged tap)
KH is 89.5 ppm (aged tap)
PH out of the tank with a test kit 6.0 Red light!!
KH out of the tank 71.6 ppm possible from the wood softening it?

Since my PH controller was set with calibration liquid on day 1, I decided to check it again...because the PH test kit read the tank water was at 6.0 but the PH controller said it was 6.5

It had not been calibrated right. It was actually calibrated to 7.5, so I corrected it. After replacing the probe into the tank the PH Controller number matched what the test kit had told me....6.0

I unpluged the unit overnight thinking the PH would raise and BUT this morning it had dropped a bit more to 5.9

I don't really have a PH in mind, but I think 5.9 is way too low. I will keep Discus and Rams so I think 6.5 to 6.8 is a good PH for me. How do I get the PH to raise and stay at the same level??

I was dosing at 2 bubbles per second but have dropped it back to 1 bubble per second and raised the PH Controller to 7.0
How long before I see a change in PH??

Thanks for any help in advance!!
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post #2 of 4 (permalink) Old 11-23-2008, 07:20 PM
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Better to leave your pH alone, there is nothing wrong with low pH unless you are keeping plants or fish that absolutely must have hard water to survive, the majority of species will adapt to pretty much anything as long as it is consistent, ... test kits are pretty iffy things to rely on unless they are the expensive type and you test the test kit using calibrated solutions... to accurately test for CO2 you need a very expensive CO2 metering device. Are you using a drop checker? I don't use a pH controller but if I did I would turn it off until I got my CO2 dialed in using a drop checker for reference (green to light yellow while watching that the fish aren't stressed) once the CO2 is dialed in test your pH and if you feel you must use the controller set it to the pH level that your test kit shows when CO2 is dialed in. If you don't have a drop checker simply raise the CO2 in small increments giving it PLENTY of time between tweaks, be home to watch the fish while you do this and at the point they start to look stressed back off on your bubble rate a bit until they look comfortable again, then test pH and set controller. With a tank as large as you have CO2 diffusion will be an issue I think you need to look at adding one or more powerheads to keep CO2 and nutrients moving through the entire water column. Not so sure that a single XP3 is enough filtration for a tank this size either.
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post #3 of 4 (permalink) Old 11-23-2008, 08:38 PM
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I really wouldn't worry about your pH being low. Your species actually may live in even lower pH waters. In addition, pH swings due to CO2 are generally nothing to be concerned about.

When it comes to CO2, you'll probably want a drop checker. A drop checker is a device that contains a small amount of 4dkH solution. It can be made with nothing more than baking soda and distilled water, but it is pretty difficult due to the precise and small measurements. It's easier to buy it, and one bottle will last a lifetime. The 4dkH solution provides you with a standard to measure pH change against. By adding the pH test solution (I think it's bromethyl blue), you can see the pH change. The drop checker keeps the 4dkH solution separated from your tank water with a small air gap. This air gap will contain outgassed CO2 from your tank water. The higher the concentration of CO2 in the tank water, the more outgassed CO2 will be in the air gap. This, in turn, will dissolve into the 4dkH solution, changing the pH and changing the color. Since the amount of CO2 outgassed and amount dissolved may vary slightly, this will give you an estimation, but a pretty good one. It is suggested that you keep your drop checker at a green color, but I turn my CO2 slightly up to a light green, almost yellow color. You may need to play with it a little. If your fish are not unhappy, you are probably fine. Don't adjust it and leave, make sure you are there for the day when you are first setting your CO2. It takes time for the checker to adjust, and you should watch your fish for a few hours when changing the CO2 level.

The only other thing I can think of is that you should be careful with snails. If you have expensive snails, long term exposure to CO2 could eat away at their shells. I will leave it to someone else to answer how to fix that.

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post #4 of 4 (permalink) Old 11-23-2008, 08:49 PM Thread Starter
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Thank you both for your information. I have 2 Rena XP3's on the tank. But the CO2 is only hooked up to one. I have a CO2 reactor but I need to replace an elbow that had a leak. I'll buy a drop checker. Again thanks.
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