pH and CO2

[ejaramillo01]

This is maybe a dumb question, but I have been going around and around, looking for the right explanations, and I'm still confuse. Pretty soon I will start to inject CO2 to my tank, it is a 100G planted. My ph is consistent at 7.6, my kh is around 7 drops, which gives me a hardness value of 125.

I always hear that changing the ph it's bad for the fish, fluctuations in the ph can kill the fish. But I read that adding CO2 will drop the ph. In fact, you need to control the ph to add or stop the injection of CO2.....???????

In few words, adding CO2 will make fluctuations in the aquarium? Good for the plants, but bad for the fish? If I add a ph meter to control the solenoid valve, how low do I need to see the ph drop to shutoff the solenoid? If my ph is 7.6, do i set it up to drop all the way to 6.8 which is the value where the ph/kh chart tell me that my Co2 levels are ideal? How do I know ?

Sorry if I confuse you with my questions...

 

[fort384]

Injecting CO2 does lower pH, but it is not the same as using a chemical additive to achieve the same effect. If you want to use a pH controller in conjunction with your solenoid, you would just set the controller to a pH of 6.8. The controller will turn on the CO2 until the pH reaches 6.8, at which point it will shut off. As the pH starts to raise again as CO2 is off gased, the controller will turn it back on. There is a deadband on most controller of at least an entire tenth, so the controller will not continually turn it on/off. Mine seems to turn on/off maybe once an hour or so when using an sms122 controller.

 

[ejaramillo01]

Injecting CO2 does lower pH, but it is not the same as using a chemical additive to achieve the same effect. If you want to use a pH controller in conjunction with your solenoid, you would just set the controller to a pH of 6.8. The controller will turn on the CO2 until the pH reaches 6.8, at which point it will shut off. As the pH starts to raise again as CO2 is off gased, the controller will turn it back on. There is a deadband on most controller of at least an entire tenth, so the controller will not continually turn it on/off. Mine seems to turn on/off maybe once an hour or so when using an sms122 controller.

Thanks Fort, by the way I will use the equipment that i bought from you.
Just let me ask you something else... if my pH is 7.6 , then I adjust the pH controler to shutoff the solenoid when the ph gets to 6.8... and so on... My pH will change in the tank from 7.6 to 6.8 ? Is this going to stress the fish?

 

[mohican]

I believe you just set the controller for 6.8 and it will keep it there automatically, turning on/off as needed. Fish can tolerate some pH swings, not just too drastic or sudden. Can someone double check me?

 

[fort384]

Thanks Fort, by the way I will use the equipment that i bought from you.
Just let me ask you something else... if my pH is 7.6 , then I adjust the pH controler to shutoff the solenoid when the ph gets to 6.8... and so on... My pH will change in the tank from 7.6 to 6.8 ? Is this going to stress the fish?

No, it will be fine. Changing the pH by CO2 injection is not the same as altering it in other ways. Especially if you use a controller, the pH will be very stable. Most folks don't use a controller and just use a timer on the solenoid and still the fish do ok, even with a swing induced by CO2 injection of as much as 1 point either way (when close to 7 of course... pH is not a linear scale).

 

[CorallineAlgae]

I use a ph controller and a drop checker with 4DKH solution. Whenever the drop checker is a nice light green I set the ph level there and the DC stays green. You can do a similar setup using a timer and just adjusting your co2 needle valve to get the bubble rate you need to keep your co2 level in the green. You won't hurt your fish and you'll help your plants, which will in turn help your fish. We have lots of ways to accomplish the same goal in our hobby but using a drop checker is pretty standard practice when using pressurized co2. It helps take some of the guess work out of it, it's a cheap insurance policy, and offers a little peace of mind. They turn blue when the co2 is low, green when it's good and yellow when it's higher than you need... all at a glance. You should be able to get one WITH the 4DKH solution online for about 12 bucks. Gotta love that!

 

[ejaramillo01]

No, it will be fine. Changing the pH by CO2 injection is not the same as altering it in other ways. Especially if you use a controller, the pH will be very stable. Most folks don't use a controller and just use a timer on the solenoid and still the fish do ok, even with a swing induced by CO2 injection of as much as 1 point either way (when close to 7 of course... pH is not a linear scale).

Thanks Fort, I got it.

I received all the parts today, except the pH controller (will arrive Mon) and the drop checker (I haven't order it yet), so I added CO2 for like 2 hours, I never saw a change in the ph of my tank, I measure it with API liquid test. I added at a rate of 1 to 2 bubbles / second. I stopped because was getting late, and the tank lights went off.

Any suggestions here, I will wait for the ph controller, but in the mean time I will just added with a timer.....
Do you think that 1 to 2 bubbles/second is good?

My tank is a 100G, and the diffuser is rated for 50G tank...

 

[ejaramillo01]

I use a ph controller and a drop checker with 4DKH solution. Whenever the drop checker is a nice light green I set the ph level there and the DC stays green. You can do a similar setup using a timer and just adjusting your co2 needle valve to get the bubble rate you need to keep your co2 level in the green. You won't hurt your fish and you'll help your plants, which will in turn help your fish. We have lots of ways to accomplish the same goal in our hobby but using a drop checker is pretty standard practice when using pressurized co2. It helps take some of the guess work out of it, it's a cheap insurance policy, and offers a little peace of mind. They turn blue when the co2 is low, green when it's good and yellow when it's higher than you need... all at a glance. You should be able to get one WITH the 4DKH solution online for about 12 bucks. Gotta love that!

Thanks, I will order the drop checker, any suggestion?

 

[fort384]

eBay has the best deals on drop checkers. You can usually find 4dKH solution too for around $5 on eBay do you don't have to go through the trouble of making it if you don't have the tools or the time.

 

[BillD]

I always hear that changing the ph it's bad for the fish, fluctuations in the ph can kill the fish. But I read that adding CO2 will drop the ph. In fact, you need to control the ph to add or stop the injection of CO2.....???????

This is further evidence that "pH shock" is another myth that has taken on a life of it's own. CO2 injected tanks that inject only when the lights are on, have daily pH swings that do no harm to the fish. The basic water parameters stay the same, in terms of TDS (Total Dissolved Solids). The supposed fish deaths attributed to pH shock are more likely the result of osmotic shock, which is real.

 

[aqua_chem]

pH is pH, hydrogen is hydrogen. Chemically speaking the pH change from chemicals is the same as from CO2 addition. But there is widely held view that pH swings from CO2 don't hurt fish, but other causes do? It's like saying that one brand of aspirin works better than an identical dose of another brand. They're both aspirin, and it's in your head.


Osmotic shock is a much better fit here than pH. I often wonder if pH is important in any facet of fishkeeping, or if it's just the correlation between pH and KH/TDS that keeps people thinking that it's important.

 

[fort384]

pH is pH, hydrogen is hydrogen. Chemically speaking the pH change from chemicals is the same as from CO2 addition. But there is widely held view that pH swings from CO2 don't hurt fish, but other causes do? It's like saying that one brand of aspirin works better than an identical dose of another brand. They're both aspirin, and it's in your head.


Osmotic shock is a much better fit here than pH. I often wonder if pH is important in any facet of fishkeeping, or if it's just the correlation between pH and KH/TDS that keeps people thinking that it's important.

Dissolving gaseous CO2 into water creates carbonic acid which lowers pH... So yes, chemically speaking it is the same effect. However, it is much easier to explain that the pH shift caused by CO2 injection is somewhat harmless to fish than to go into the relationship of H+ or OH- and carbonic hardness, ionic concentration, permeability, osmosis, and what happens when attempting to buffer water with chemical solutions of CaCO3, etc. Technically it would be osmotic shock that causes problems, and the claim that pH swings from CO2 are different is a fallacy, but it is a simple way to explain why we care so much about stable pH normally, but not when it comes to CO2 injection. There are many such fallacies in the hobby (for example the constant recommendation of color temperature instead of talking about wavelength), but for most the over simplified version is really all folks are looking for, and generally speaking, a lot of the time the results are what is important, not necessarily the process of how we got there. But maybe it isn't the right way to go...

 

[Jscoggins]

So what is "Osmotic Shock"..is it caused by the chemicals used to change the ph?

Never have heard of this before you guys are blowing my mind...against everything I have ever learned in the past..

Boy you guys know your stuff!!!!

 

[Jscoggins]

So what is "osmotic shock"....I have never heard of that before..Is it caused by the chemical they use to lower the ph..instead of it being more natural like co2?

 

[fort384]

Osmotic shock simply is what happens when you dump a bunch of ions in water where there was a lower concentration of ions before (or the opposite, rapidly lowering the concentration of ions also causes osmotic shock).

Water inside the cells of animals have a certain concentration of solids (ions). Because of osmosis, the water inside the cell is constantly passing through the semipermeable cell membrane to reach equilibrium with the concentration of ions in the water outside the cell. If a rapid change in ions occurs, i.e. a bunch are added to the water, the water inside the cells rushes out through the permeable membrane to try and reach equilibrium (same concentration on both sides of the membrane).

It isn't a question of natural or not. pH is a measure of the concentration/activity of H+ ions in solution.

 

[ejaramillo01]

Ok I got everything installed and working... Milwaukee SM122 PH controller, CO2 rate at three bubbles/sec. The only thing missing is the drop checker (will be here tomorrow)

Final questions:

My GH in the tank is at 5 drops.. This means that my ideal pH will be 6.8, so I calibrated the pH controller and I will try to set it up to stop the solenoid once the ph reach 6.8......
This means that now my CO2 system will be constantly on and off? Even when the lights of the tank are off during the night?. I understood that I will need the CO2 when the lights were on... Because is when the plants will use the CO2 ..... Am I missing the point? Is my tank now will have between 20 to 30 ppm of CO2 all the time with the controller?

Sorry for all these final questions....

 

[ejaramillo01]

Ok I got everything installed and working... Milwaukee SM122 PH controller, CO2 rate at three bubbles/sec. The only thing missing is the drop checker (will be here tomorrow)

Final questions:

My GH in the tank is at 5 drops.. This means that my ideal pH will be 6.8, so I calibrated the pH controller and I will try to set it up to stop the solenoid once the ph reach 6.8......
This means that now my CO2 system will be constantly on and off? Even when the lights of the tank are off during the night?. I understood that I will need the CO2 when the lights were on... Because is when the plants will use the CO2 ..... Am I missing the point? Is my tank now will have between 20 to 30 ppm of CO2 all the time with the controller?

Sorry for all these final questions....

I forgot to add that I keep my light on just for 5 hours a day, I have three bulbs t5 HO Giesseman Aquaflora 6,500 K with 54W each.

 

[aqua_chem]

I would recommend measuring your pH without any CO2 in it, and setting your probe to 1 pH unit below that. That should give you 30 ppm or so of CO2. If you need more (and you may), then you can adjust from there.


Also, you should have your lights on longer than that. 8 hours is a decent starting point.

 

[ejaramillo01]

I would recommend measuring your pH without any CO2 in it, and setting your probe to 1 pH unit below that. That should give you 30 ppm or so of CO2. If you need more (and you may), then you can adjust from there.

Also, you should have your lights on longer than that. 8 hours is a decent starting point.

Thanks. I will increase the lights also.

 

[ejaramillo01]

Thanks, sharing

Thanks to all, I started the CO2 injection in my tank 3 1/2 weeks ago... Added the pH Controller, the drop checker, everything has being smooth. The plants took off immediately... The banana plant grew a steam, all the plants turned healthy, the algae is going down, still I'm seeing some, but getting better.
here are some pics of the tank: