CO2 levels with pH controller
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Old 06-10-2013, 04:40 AM   #1
Fujiija
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CO2 levels with pH controller


Hello - I am reposting a different question from a previous thread.

I got my inline CO2 diffuser working with a pressurzied CO2 system. At 2 bps, I can see a fine mist coming out of my spray bar.

I borrowed a pH controller that was calibrated. I have run my CO2 diffuser for two days and I cannot get the pH below 7.5 at 2 bps. The pH controller never shut off and my CO2 has been running constantly for two days, even at night. My tank water started at pH 8.3 before CO2 injection. My kH is 120ppm and GH somewhere about 150.

My tank is 45 gal with Fluval Stratum, 3x39w T5HO, heavily planted with lots of fish. I had been running CO2 through an airstone and just recently moved to the GLA inline CO2 diffuser.

Why does my pH not go below 7.5? Do I need to increase the bps? At 2 bps, my tank seems to be burning through CO2 more quickly than when I ran my airstone. After reading posts from others, I figured I should get my pH down much lower (e.g. 6.8) in a matter of hours at 2 bps but that never happened.

Any ideas would be appreciated.
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Old 06-10-2013, 08:22 AM   #2
theericafish
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I use different test kits which read in degrees for kh and gh but from what I understand 120ppm of kh is 6.7 degrees of kh.

With that kh and ph, according to the kh/ph/co2 correlation charts you only have about 7.1 mg/l of co2 in your tank.

The goal is around 30 mg/l. So you want to get your ph down to around 6.8.

You may not have enough bps, or you may have too much surface agitation.

In my opinion as long as you aren't running into algae issues, your fish are breathing and acting normal and your plants are growing quickly, hitting exact levels of co2 is not completely 100% necessary.

Ph controller is not as necessary as it is a safety net that will keep your co2 from suffocating your fish. It also is only efficient if the way you are diffusing the co2 into the tank is efficient. For example if the bubbles are just floating to the surface and escaping your co2 will never turn off, and you will never reach optimum levels of co2.

Surface agitation should be kept to a minimum if not yet done. It should be a slight ripple, but not splashy of any kind. Once that is accomplished if co2 levels do not rise, up the bubbles per second. Make sure you do not leave the house after messing with co2, observe the tank and livestock.

Additionally the flow is very important, you should be attempting to keep the co2 bubbles in the water as long as possible to maximize the amount of co2 being diffused into the water. The only difference I see between regular diffusers(glass/plastic/chopstick/airstone/etc.) and in line types is simply that you have an easier time aiming the flow of where the co2 bubbles actually go. On the other hand a reactor type diffuser actually increases the efficiency of co2 being dissolved into the water.

It seems there is some debate as to which type of diffusion is more efficient for plant growth. Co2 bubbles sticking to plants or no bubbles and adequate co2 levels in the water. Both seem to work anyway, so it comes down to if you want to see bubbles or not. Reactor types seem easily more efficient but with the right flow and an in line reactor I'm sure you can have the same results.
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Old 06-10-2013, 01:19 PM   #3
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I have surface agitation but no splashing with my spray bar.

I have now reangled my spray bar to a 45 degree down slope towards the front of the tank. The spray bar is across the top back of my tank.

I have read many other posts saying how they love the GLA inline diffuser. I am now wondering if 2 bps is not enough flow or maybe I still have a leak in my system and I really should be seeing more fogging. I see some fog but you have to look really well to see it. At this rate of running 2 bps all day and night, I can see I am burning through my pressurized CO2 tank (don't know the size of the tank, but it's about 18 inches tall).

I am not sure if I will buy a pH controller at this point as I can't get my pH down.
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Old 06-10-2013, 02:24 PM   #4
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With the ph controller you dont have to worry about bps. You have to worry about how well you can dissolve your co2. Your controller will shut off your solenoid when the desired ph is reached.

The ph you want to reach is a big drop from your resting ph. Your aim should be one point lower than what your resting ph is. This is only if your livestock can withstand a one point drop. Mine cannot i can only go 3/4 ths of a point before they hit the surface.

If you want to bring your ph that low you will need to soften your water.
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Old 06-10-2013, 03:27 PM   #5
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Thanks for the input. I've read postings on this forum that warn against monkeying around with chemically softening my water unless I go with RO water (which I really do not want to do at this point).

I also emailed GLA again and asked what they thought.

Here's what I plan to do:

Change out the spray bar and put on a nozzle instead
Continue to run at 2 bps, but ditch the borrowed pH controller since it does not look like I can really get that much CO2 in my tank due to water hardness
Run my solenoid on a timer instead and just run the CO2 maybe a hour before the lights go on and have it turn off when my lights go off

I figured this may be the best compromise given I cannot get to 30ppm CO2 because my water is too hard.

Sigh. I guess I learned something by borrowing the pH meter/controller. My plants actually do well and my fish are happy at whatever I had been doing before. So I should just accept that and stop trying to get to the holy grail of 30 ppm CO2 and pearling plants.
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Old 06-10-2013, 03:42 PM   #6
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I keep my co2 levels at 6.2. Its a 45 gal heavy planted. At around 5.9 the fish come up for air. My plants start pearling within the first hour of the light being on. I also have a diy co2 diffuser though. Its very efficient but takes a while to drop ph, so I turn my ph controller on many hours before. Before you go anywhere, you need to find a very efficient diffuser. I dont know how good those bubble disk diffusers are. I used to hook my co2 line into my powerhead and it used to break them into tiny bubbles and throw them all the was to the other end of the tank. That was a good one but not efficient enough. In terms of that, the disk will be less efficient than that because the bubbles just float up. They need to be under strong current.
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Old 06-10-2013, 07:52 PM   #7
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Quote:
Originally Posted by Fujiija View Post
Thanks for the input. I've read postings on this forum that warn against monkeying around with chemically softening my water unless I go with RO water (which I really do not want to do at this point).

I also emailed GLA again and asked what they thought.

Here's what I plan to do:

Change out the spray bar and put on a nozzle instead
Continue to run at 2 bps, but ditch the borrowed pH controller since it does not look like I can really get that much CO2 in my tank due to water hardness
Run my solenoid on a timer instead and just run the CO2 maybe a hour before the lights go on and have it turn off when my lights go off

I figured this may be the best compromise given I cannot get to 30ppm CO2 because my water is too hard.

Sigh. I guess I learned something by borrowing the pH meter/controller. My plants actually do well and my fish are happy at whatever I had been doing before. So I should just accept that and stop trying to get to the holy grail of 30 ppm CO2 and pearling plants.
You can reach 30 ppm co2 with hard water.

Here is how you set your ph to reach 30 ppm.

1 cup of tank water let it set for 24 hours.
Test what ph is after 24 hour rest.
Ph = 8
You would want to reach a ph of 7. A one point drop should give you 30 ppm.



I use this method every time i calibrate.
My plants pearl within an hour of lights on.
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Old 06-11-2013, 12:06 AM   #8
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I do the 1 point ph drop thing too. But you have to be careful and creep up on it.

The 1 point drop stems from the fact that 1 point is a 10 times increase in CO2, and theory says that water in equilibrium with air will have a 3ppm CO2 concentration. Hence, 10 times 3 is 30ppm.

However, if there are fish in the tank, they exhale CO2 and thus the concentration of CO2 could be higher than 3ppm in equilibrium. In which case, a 10 times increase is over 30ppm.

So creep up on it slowly and watch your fish.
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Old 06-22-2013, 02:50 AM   #9
Fujiija
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I've been thinking - could it be possible that my tank is so heavily planted that it is using up all the CO2 and hence my pH cannot drop very far? You can see in my posting a photo of my tank. If that is the case, then I need a better CO2 diffuser for a 45 gallon tank and not use the GLA inline diffuser? Or as others have mentioned, just run the CO2 at something greater than 2 bps? I am still stumped.

I am all ears of those who use diffusers.
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Old 06-22-2013, 04:11 AM   #10
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Quote:
Originally Posted by Fujiija View Post
I've been thinking - could it be possible that my tank is so heavily planted that it is using up all the CO2 and hence my pH cannot drop very far? You can see in my posting a photo of my tank.
Looking at the photo, I would say, no.

But at the same time it's very strange that you get so little CO2 dissolved.
pH 7.5 at 6.7 dKH is just about 7 PPM of CO2.
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