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Discussion Starter · #1 ·
So I'm having trouble finding information specific to my problem, and thought I'd give a new thread a shot. I'm curious to know exactly how safe it is on the fish and plants in general to boost the CO2 as high as my fish are comfortable with. Water coming out of the Tap is about 7.6 PH, and I have been slowly raising the amount of CO2 in the tank weekly to the point to where my PH controller is set to turn everything off at 5.7ph. I have yet to see any signs of my fish having issues with the water. I like having the peace of mind the PH controller gives me in case something were to go wrong.


  1. Should I keep adjusting the ph controller to go lower in order to maximize the amount of CO2 I have in the tank?
  2. Is it good practice to have the PH controller constantly turning off the system once it gets to a certain PH, or should I be trying to find a setting to where the CO2 is constantly on? Does it even matter?
 

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For most, the common thinking is that the "ideal" of 30PPM CO2 is reached when you have dropped PH by a full point. But that can be effected by the tank water parameters like GH/KH. Not an exact science? How the fish react will vary. Part of it with my fish seems to be how slowly I run it down but I deal African cichlids and get them down to close to a full point. About 6.8 is as low as they allow.
I would think you have actually gone a fair way past ideal?
Your results may matter on which controller and how close it keeps the PH. How far off the setting does it let things drift? If it drifts two tenths, I say no worry but if it drifts two full points and then adjusts, I don't go there as it seems to be more stress than needed for the fish to constantly adapt.
Given time, it may be easier to see what the plants/algae and fish all do on the results when watching but for most that is a real challenge. I still can't say that I can look at my tanks and spot a solution for a problem. It's very much an adjustment here and there to see what might work better.
 

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OP. It is very simple. Start low and ramp up slowly. When your plants start pearling hold that bubble rate or amount for a week. If no algae appears and your dosing stays the same then you are good. If algae appears then you need to up co2 SLOWLY.

If your co2 levels are correct it will boost the growth of your plants and they will outcompete the algae for nutrients.

Watch your tank and stop chasing numbers.


Sent from my iPhone using Tapatalk
 

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You can't use the pH of water as it comes from the tap for anything, except assurance that your water company is keeping your water and plumbing safe. The pH that matters is what the tap water pH is after it has been out of the tap, exposed to the air, for a day or two. Normally that is significantly lower than the "out of the tap" pH. So, you may be dropping the pH with CO2 by less than 1.0. If you take a water sample from the tank, and let it set out in the open for at least a day, then measure the pH, that will be a better starting point when looking for a 1.0 pH drop. Or, just measure the tank water pH just before the CO2 comes on, and use that for the 1.0 pH drop check.

30 ppm is not a magic CO2 concentration. The lower the light intensity, the lower the CO2 concentration can be and still help the plants. And, the higher the light intensity, the higher the CO2 concentration has to be to provide enough for the plants faster growth rate caused by that light. To find the optimum concentration for the plants you have to raise the concentration a small amount every few days and watch the plants to see if they grow better. If they do, another small increase might be even better. If they don't, you don't need a higher concentration. Eventually you reach a concentration too high for the fish to tolerate, so that limits how high you can go.
 

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I run my CO2 using a ph controller. My tap water PH is fairly low and very low KH, so I have the pH controller set to 5.2. I try to adjust the CO2 injection rate so that it stays consistently on, but it does turn off several times throughout the day due to the pH controller once the water is saturated with CO2, and will then come back on accordingly. I initially determined the 5.2 ph level until my drop checker starts to turn yellow-ish (high concentration) and yet while the fish are still acting normally and not gasping.

My understanding is that as far as fish's pH preferences go, the pH alteration from CO2 injection is not the same and doesn't effect the fish being in a "too low" ph environment (go off of what your water's ph is before CO2 injection as far as fish preferences go). The concern with the fish is just not gassing them out, not the ph level. I have cardinal tetras, roseline sharks (who are very sensitive fish to oxygen/co2 levels), SAEs, amano shrimp, cherry shimp (while they last, they get eaten by roseline sharks), otos, etc. I've had a some various barbs over the years as well and I've never had a problem with any fish and the CO2.
 

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I'm new to using a controller too. I bought 15 otos and the controller had been set to go off 6.05 and to come on at 6.0. All but one died, but the one survivor is doing great.

I am starting to think it doesn't matter as long as you give new animals time to physiologically adapt. My drop checker is yellow but the oto seems as happy as can be. I guess he was just particularly resilient.

I will obviously replace the otos, but I am thinking if I set to controller to 6.5 and knock it down a point daily, or even better every other day, that by the time I am to 6.0 again they should all survive.
 

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Discussion Starter · #7 ·
I understand the PH is related to the amount of CO2 in the water, but does this value still hold true if your PH controller turns everything off once it gets to its cut off setting? Just curious why I've read several occasions where people say your co2 should be blowing constantly. I have mine set to turn off at night though since there is no point in running it then.
 

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I understand the PH is related to the amount of CO2 in the water, but does this value still hold true if your PH controller turns everything off once it gets to its cut off setting? Just curious why I've read several occasions where people say your co2 should be blowing constantly. I have mine set to turn off at night though since there is no point in running it then.
My pH probe holds it's calibration after it's turned off/on. So if you turn it off at night that's fine, it won't hurt anything. When it turns back on it will inject CO2 until it reaches the desired level again. I just let it run 24/7 though and noticed it will do it's job... since the plants aren't using CO2 at night it will use much less to keep it at the set pH level. This way the tank is always 100% ready and at the desired CO2 levels, although if you turn it back on with enough time to reach the desired CO2 levels by lights on that should be fine as well and maybe save a little bit of CO2... Im just too lazy for that... set it and forget it.
 

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The idea behind using a controller is to keep a constant saturation level of CO2 and avoiding pH swings. I used one for a few years, but keeping the probe calibrated was a pain, and the controller consistently had issues with false readings that resulted in gassing my fish. I'm no longer using it and have decided to leave the co2 on a timer instead.
 
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