New To Co2, Have Some Questions

  • #1
Hello everyone. I just recently set up my first planted aquarium with co2 and I had some questions because I don't want to wake up one morning to a tank of gassed fish.

So I purchased a co2 system with azoo regulator and milwaukee mc122 controller. I purchased a high end KH test kit and determined the KH value of my water to be 3.8. I was told to look at a ph-kh chart to find the ideal ph range for my aquarium kh which happens to be between apx 6.6 and 7.0.

So I believe it goes as follows: as co2 is injected into the aquarium it will lower the ph and increase the co2 ppm, which you don't want the ph to go below 6.6 or above 6.9 because it would then go outside of the optimal range determined by the KH levels? Is this correct or am I missing something?

I set my regulator to kick off once ph levels reach 6.7 (as a precaution because I still don't trust the controller 100%.) If this is the case, that means I really don't need to run a timer in sync with the lights because the co2 will shut off once the ph reaches 6.7 regardless. The whole reason of running it in sync with the timer is so the co2 doesn't gas the tank while plants aren't photosynthesizing. Is this correct as well?

And to finalize the reason for doing all of this and running a controller is to ensure c02 ppm determined by the ph won't reach lethal levels, but will always be high enough to provide maximum co2 for plant growth?

Do I have all of my information correct here? Does anyone have any tips for me? Thanks in advance
  • #2
While it all seems correct, I would test your current pH. I would base your controller ranges off of that. Fish are rather tolerant of different pH ranges, but they aren't tolerant of sudden pH changes. If your current pH is for example 7.8, having your controller set around 6.6-6.9 would probably be pretty lethal. If it was 7.2 right now, that would make more sense. Sorry, I'm not very familiar with kH stuff, so if you already know what the current pH is and everything is pretty close, it should be fine. As always though, I would recommend starting out slow when injecting co2. Just out of curiosity for my setup, what controller are you using? I've been looking for one but I've only found ones that are over $100, which I don't want to spend.
  • #3
For me when I used a controller, I used a drop checker primarily to control my controller. What I mean, lower the controller pH dial until drop checker turns green. It’s a trial and error for a day or so to get things dialed in. Keeping your probes properly calibrated will keep your tank relatively steady and near this range. Your inhabitants should be fine. You can use the pH/KH chart to get an idea (getcha started) but I based things off my drop checker.
  • #4
Agree with the above; I find ph/kh charts much too complicated and leave too much room for inaccuracies. Buy a drop checker and adjust your CO2 output until the drop checker is green. Don't worry about ph, fish tolerate ph fluctuations from CO2.
  • #5
I have a similar setup to yours Loffredom so I can relate to what you are saying.
My CO2 system is designed to regulate my pH, so I too inject CO2 to lower my pH in a 120 gallon tank. In my experience the balance I needed to find was between the amount of aeration of the water (be it surface ripples or pumping air via a stone) and the injecting CO2.

The way I do it is to inject CO2 based on the pH level only (6.85-7.05) irrespective of the time of day, and then allow the air pump to reduce the CO2 (pH) level in the water at night. I admit that there are times when both CO2 is being injected and the air pump is running around 5-7 am, however I don't try to regulate the precisely as the additional CO2 available in the water as soon as the lights go on is good to kick start the photosynthesis cycle. So I hear what you are saying, but I don't bother with as the airstone also provides more water circulation in the tank, which is important for me with a big tank.

Recommend that you read this post I made on CO2 - it took me over a year to realize a mistake I was making, so a ten minute read will save you a lot of hassle!

The other thing I would like to share, is that we sometimes forget that the pH scale is actually a logarithmic scale. What that means is that a jump from a pH of 6 - 7 is actually 10 times more acidic and not just one time more acidic. So it is recommended to regulate narrow (just like you are doing Loffredom edom) to avoid spiking.
  • #6
I don't have a pH controller to monitor CO2 injection because I don't believe that pH changes due to fluctuating CO2 level are dangerous to fish. However, a very low pH can increase the solubility of certain rocks, shells or decorations you might have in your tank and THAT will increase GH which is more dangerous IMO. Very low pH might also stall the biofilter but who needs a biofilter if you have healthy growing plants?
Another interesting thing to keep in mind is that plants are quickly consuming all available CO2 in one continuous process. Once the levels are depleted, photosynthesis stops and it will not restart for the same photoperiod. A period of rest (darkness) is needed. During that time, plants will give off some of the CO2 that was assimilated during the day. For that reason, I personally prefer to load the tank with CO2 before lights are coming on. I start injecting at 7AM and light are on at 9AM. CO2 is off at 1PM, lights are off at 5PM. It works for me but I understand why this should not be a general rule. Every tank is different: you cannot expect a tank with few slow growing plants to work the same way as one with lots of fast growing plants. I accidentally overdosed CO2 on more than one occasion and no fish died. I have few ideas why but I am not certain.
  • #7
a very low pH can increase the solubility of certain rocks, shells or decorations you might have in your tank and THAT will increase which is more dangerous

What do you consider a very low pH aniroc ?
  • #8
Less than 6.5 would be low, less than 6 is very low.

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