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Discussion Starter · #1 ·
Hi All--New to the forum, please let me know if this should be posted elsewhere--

Despite a few decades in the hobby, this is my first fully planted tank with medium/high light and CO2 injection, so I have LOTS to learn--

I set up a 40 gallon breeder about three weeks ago. Planted it 10 days ago. I have CO2 injection with a pH controller. No fish yet, but the plan is to keep wild caught Betta sp. so a pH around 6 would be fine. My source water is pH 6.5 and even when I set the pH controller to add CO2 until the pH hits 5.5 my drop checker shows that I am below the ideal CO2 level for plant growth. Although the Bettas would be fine at pH 5.5, I would like to add a few species that might be happier at pH 6.0, and in any case, the drop checker (brand new with fresh indicator fluid) is indicating I am not getting enough CO2 into the tank even if I drop pH to 5.5.

I am not sure what adjustments I need to make in order to add sufficient CO2 for the plants and keep the pH from dropping below 5.5. Ideally I would prefer to maintain it around 6 during the day.

Thanks for any suggestions!
R
 

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get a pH pen and dump the drop checker. the pen will give real-time approximation of co2 concentration. drop checkers let you know what your pH WAS 2-3 hours prior.

also, what is your kh?
 

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Discussion Starter · #3 ·
Thanks Moke-- A quick check of the web makes me believe a pH pen is the same as a portable pH probe, let me know if I am missing something there. My Milwaukee ph Controller has a stationary pH probe (which can be moved, but generally doesn't) which is measuring pH at 5.4, (which is why the CO2 solenoid shuts the CO2 off). I also have a hand held pH probe that measures the pH to within a hundredth or two of the stationary probe when put in the same area of the tank and as high as 5.6 on the opposite side of the tank. (For what it is worth the drop checker is within about 5 inches of the stationary pH probe.)

I have a kh test kit, but haven't used it since I am unclear on how to best interpret such a test. I can test kh next time I am at home and post the results for comment.

Thanks again for your response.
 

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The pH drop from injection of CO2 is not the same as changing the dKH to alter pH.

Just turn up the CO2 and adjust your pH controller to drop pH a bit lower. I drop mine from 6.25 to 4.85 daily with a full tank of Rainbowfish.

At a one point drop in pH a drop checker is usually green. At about 1.2 it's usually lime green, and at a 1.4 drop like mine it would be pure yellow.
 

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My source water is pH 6.5 and even when I set the pH controller to add CO2 until the pH hits 5.5 my drop checker shows that I am below the ideal CO2 level for plant growth. Although the Bettas would be fine at pH 5.5
You have to test your degassed aquarium PH an not your source water PH. Things in your aquarium could lower your KH/PH. Best thing to do would be to take water from your aquarium in a bottle, shake it up, let it sit a minute, test the PH then repeat the shaking until you get a consistent PH value. This would be your starting PH point then try the 1 point PH drop from there and should give you the right amount of CO2.
 

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I had the exact same issue in one of my tanks. Tank pH before I even started injection was pegged at 6.2 for weeks. I pulled a glass, let it sit 36hrs and it tested 6.6pH. My controller was set to close the solenoid at 5.5 as well. A nice 1.1 drop, except my tank would never get past 6.1. Injection is only on 6hr/day. Wake up and check in the AM, with relay unplugged, and the monitor still reads 6.1, 30min before CO2 comes on, still 6.1. I believe the fix for me was more surface agitation at night; there's probably not enough off gassing. Some livestock though are really not happy in that much movement.
 

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Discussion Starter · #8 ·
You have to test your degassed aquarium PH an not your source water PH. Things in your aquarium could lower your KH/PH. Best thing to do would be to take water from your aquarium in a bottle, shake it up, let it sit a minute, test the PH then repeat the shaking until you get a consistent PH value. This would be your starting PH point then try the 1 point PH drop from there and should give you the right amount of CO2.
Thanks Gorrillastomp--Yes, I have a substrate and driftwood both that might pull the pH down from the 6.5 the water is when I add it to the tank. The gist of these comments seems to be I should be fine with letting the pH drop below 5.5 if that is what is needed to get sufficient CO2 added.

I had the exact same issue in one of my tanks. Tank pH before I even started injection was pegged at 6.2 for weeks. I pulled a glass, let it sit 36hrs and it tested 6.6pH. My controller was set to close the solenoid at 5.5 as well. A nice 1.1 drop, except my tank would never get past 6.1. Injection is only on 6hr/day. Wake up and check in the AM, with relay unplugged, and the monitor still reads 6.1, 30min before CO2 comes on, still 6.1. I believe the fix for me was more surface agitation at night; there's probably not enough off gassing. Some livestock though are really not happy in that much movement.
Thanks tuphatDimes--Yes, I can see that my problem is likely more complicated than just letting things go to a lower pH will fix. Off gassing is likely a big problem because the tank has a cover (cats in the house that I have no desire to turn into catfish) and not a ton of surface agitation since I am hopeing to spawn bubble nesting bettas. That combination could make it really hard to inject CO2 in sufficient quantities (unless someone here has worked these problems out before)
 

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Thanks tuphatDimes--Yes, I can see that my problem is likely more complicated than just letting things go to a lower pH will fix. Off gassing is likely a big problem because the tank has a cover (cats in the house that I have no desire to turn into catfish) and not a ton of surface agitation since I am hopeing to spawn bubble nesting bettas. That combination could make it really hard to inject CO2 in sufficient quantities (unless someone here has worked these problems out before)
Don't worry about the tank off gassing overnight. I don't know of a tank that does and it's not something you need to be concerned about and is not a goal of a planted tank.

Keep in mind that CO2 and O2 are not mutually exclusive, and in a healthy tank you want high levels of each. I mention that as you said you don't have much surface agitation. You should. It's better for both fish and plants. In the scheme of things CO2 is cheap so treat it like it's free.

If you want to find your true degassed pH, test both the tap and tank water. You can start by testing the dKH of each. If they are the same, then likely so is the pH.

Next leave a glass of each sample out for about three days (or 1 day with vigorous bubbler). Then start testing the pH about every 4 hours or so. Hopefully you have calibrated your probe. Be sure to leave the probe in for a decent long time (15 min) so that the reading stabilizes. Once you get the same reading four hours apart then the sample has come to equilibrium with the atmosphere. Take your time. It's worth it to get it right.

If you know your dKH you can have a pretty good idea of what it should be. Most times a fully degassed sample will have about 3 to 4 ppm CO2 at equilibrium.

If your source really is 6.5, then your source water is very soft, which is a good thing. I would expect it to be less than 1 dKH.
 

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Don't worry about the tank off gassing overnight.
Off gassing is probably not the right terminology but, in my situation I did not have enough surface agitation to release sufficient CO2 to reach a level consistent with my degassed sample before the solenoid timer started a new cycle. I was able to achieve the 1 point drop by re-configuring my return from the canister.

wild caught Betta sp.
Store bought DI water?
 
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