# [Wet Thumb Forum]-C02 Injection, PH, Buffering



## shogsten (Mar 17, 2005)

I'm mostly a lurker here but I've run into a problem that I need an answer to. I'm injecting C02 (20lb tank) and I'm trying to drive my C02 up to a consistent 30 ppm or slightly higher but I can not get my PH below 7.2 (KH 17.5 degrees) and keep it there. Overnight I can drive the PH down to 7.2 but as soon as the lights come on it starts slowly rising until I hit a high of 7.5-7.6 mid/late in the afternoon. Yesterday I added a second reactor (5 bubbles a *second* at each reactor 10+ bps at the bubble counter attached to the C02 cylinder) even with the lights out I can't get the PH below 7.2. This is my first light cycle with two reactors but I can see right after lights on it jumped to 7.3.

Well Water (comes through a softener)
PH - 8.4 (takes 48hrs to reach this)
GH - 5
KH - 17.5 degrees
Water comes through a softener.

Tank Water (150g tank)
PH 7.2 - 7.6 (PH Controller and Test Kit)
GH - 8 ( I add some MgS04)
KH - 17.5 degrees

Tank
400 watts PC 10 hours a day
20 tetras, 2 corries, 8 otos, 2 yoyo
Lots of ramshorn and mts snails
Anacharias
Anubias
Swords
Red Myrio
Hornwort
Luwidgia
Crypts 
Vals - lots and lots of vals

Why can't I hold a steady PH and why can't I go below 7.2? Is there something in my water buffering it. The reactors are working - either one will drive the PH to 7.2 by itself. Just in case there are questions on the reactors, they are 14 inches long, 2 inch ID, 8 bio balls, C02 injected 3 inches up from the bottom and 145 gph powerheads injecting at an angle at the top to get good swirl. There are very few extremely fine bubbles escaping from the bottom so the 5 bps are getting dissolved. There is very little surface agitation (a film develops over most the water). I do have a very small HOB filter I use for dissolving dry ferts but turning it off doesn't make a measurable difference. Most of the plants are growing well. I have a serious algae (hair, string, BBA) problem at this point and I'm trying to stabilize the PH and CO2 to see if that will help. All of the other tank parameters are inline with the EI method. so let's focus on my C02 issue.

Scott Hogsten


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## shogsten (Mar 17, 2005)

I'm mostly a lurker here but I've run into a problem that I need an answer to. I'm injecting C02 (20lb tank) and I'm trying to drive my C02 up to a consistent 30 ppm or slightly higher but I can not get my PH below 7.2 (KH 17.5 degrees) and keep it there. Overnight I can drive the PH down to 7.2 but as soon as the lights come on it starts slowly rising until I hit a high of 7.5-7.6 mid/late in the afternoon. Yesterday I added a second reactor (5 bubbles a *second* at each reactor 10+ bps at the bubble counter attached to the C02 cylinder) even with the lights out I can't get the PH below 7.2. This is my first light cycle with two reactors but I can see right after lights on it jumped to 7.3.

Well Water (comes through a softener)
PH - 8.4 (takes 48hrs to reach this)
GH - 5
KH - 17.5 degrees
Water comes through a softener.

Tank Water (150g tank)
PH 7.2 - 7.6 (PH Controller and Test Kit)
GH - 8 ( I add some MgS04)
KH - 17.5 degrees

Tank
400 watts PC 10 hours a day
20 tetras, 2 corries, 8 otos, 2 yoyo
Lots of ramshorn and mts snails
Anacharias
Anubias
Swords
Red Myrio
Hornwort
Luwidgia
Crypts 
Vals - lots and lots of vals

Why can't I hold a steady PH and why can't I go below 7.2? Is there something in my water buffering it. The reactors are working - either one will drive the PH to 7.2 by itself. Just in case there are questions on the reactors, they are 14 inches long, 2 inch ID, 8 bio balls, C02 injected 3 inches up from the bottom and 145 gph powerheads injecting at an angle at the top to get good swirl. There are very few extremely fine bubbles escaping from the bottom so the 5 bps are getting dissolved. There is very little surface agitation (a film develops over most the water). I do have a very small HOB filter I use for dissolving dry ferts but turning it off doesn't make a measurable difference. Most of the plants are growing well. I have a serious algae (hair, string, BBA) problem at this point and I'm trying to stabilize the PH and CO2 to see if that will help. All of the other tank parameters are inline with the EI method. so let's focus on my C02 issue.

Scott Hogsten


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## Jabopa (May 4, 2003)

Shog,
What type of substrata are you using? Is there any kind of wood in the tank? Rocks? It sounds like something is buffering the water.


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## Roger Miller (Jun 19, 2004)

How are you counting 10+ bps (or 5 bps, for that matter)? I don't think I would even be able to see distinct bubbles at that flow rate.


Roger Miller


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## aquabillpers (Apr 13, 2006)

This is a question rather than an answer.

The KH is 17 degrees. I wonder if that could be keeping the pH high, even though there is more CO2 dissolved in the water than the chart indicates? 

(The suggestion is that very high KH might invalidate that shown on the chart.) 

Is there a practical maximum to the KH, above which plants won't prosper?

Bill


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## shogsten (Mar 17, 2005)

Roger I pulled the C02 tube from the reactor, put my thumb over it, held it to the bottom of the tank and counted 1 - 1000 and looked at the number of bubbles in the water column. Not very scientific and perhaps off slightly one way or another. Anyway the bubble rate is high and I appear to be getting pretty good dissolution of the C02. I doubled the number of reactors (from 1 - 2), increased the bubble rate to both, and still my PH is at 7.2 . I'm going to pull one of the reactors back out of the 150 tonight (PH back up to 7.6) since it's not doing anything for me and setup a 20 gallon quarantine tank and do some playing and see if I can move it below a PH of 7.2. FWIW it takes my tap water a couple of days to climb to 8.4, in 24 hrs it goes to around 8.0 then after 48 hours it gets to 8.4. Could this possibly be a clue ? Somethings not right and I don't want to throw anything at the fish and plants in my 150 until I know what the heck is going on.


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## imported_shalu (Feb 13, 2004)

Simple question about your controller: is the ph probe close to the reator output? What is the ph target of controller? When ph is at 7.5-7.6, does the solenoid stay on all the time?


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## Roger Miller (Jun 19, 2004)

Bill,

There is no practical upper limit on the upper end of the KH where the curves are reasonably valid. The curves are probably not valid if the pH is over about 8.4 at any KH, but that is a different problem.

Shog,

With a KH of 17.5 your CO2 levels are high enough to make your plants quite happy -- even if the pH is up at 7.6. I know it isn't your target level, but it should grow your plants anyway.

That's an interesting approach to counting bubbles. When you stop the flow from the tube the CO2 pressure builds up in the tubing. When you release it the extra pressure gives you a larger flow rate then you normally have. Even if your count is right it will be for a flow rate that is higher than the normal flow rate. I don't know how much higher than normal, but it's conceivable that your count is several times higher than the normal flow rate.

I feed my 150 just over 1 bps directly into the intake of the Eheim. When last I checked that gave something in the range of 15-20 ppm of CO2. You're feeding up to 10 times that much and at a pH of 7.6 getting no more CO2 dissolved into the water than I am. The most obvious thing to suspect is that your CO2 reactor(s) are not dissolving the CO2.

What happens if you limit the bubble rate to something like 2 bps? If nothing else that rate can be accurately counted in a normal bubble counter.


Roger Miller


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## shogsten (Mar 17, 2005)

Roger I was at around 2 bps before all of this started. I've been slowing increasing the bubble count and went a little nuts yesterday <G>.

The strangeness continues however. When I got home last night the PH was 7.6 and just before lights out it was 7.5. One hour after lights out it was down to 7.2. I was going to move my quarantine tank over to the main tank and fill it when I found a couple of missing 5 gallon buckets in the stand of the 20.

I filled a bucket with tank water - PH rose to 7.3 - I put the reactor and PH probe into the bucket and in about 20 minutes pulled the bucket down to PH 7.1 and after an hour I got it to 6.9. I was thinking at this point that I was going to have to improve my reactor(s) in the main tank. When I went to return the reactor to the tank I noticed a couple of fish gasping at the surface and when I returned the PH probe to the water the PH was 6.9. Never in the past month have I been able to get the tank this low and I did it with the one original reactor (other reactor was in the 5 gallon bucket). I double checked everything and even recalibrated the PH probe again. The PH controller and an a brand new AP PH (9/04 mfg date) kit agree with each other. The probe responds almost instantly to the 4.0 and 7.0 solutions.

This bugged me all night so early this morning (5am to be exact) I filled another bucket with tap water (ph 7.2) and I put the reactor in and went back to bed (5:25 am). I checked the water in the bucket at 8:30 just before I left for work and it was at ph 7.2. It really does appear that I may have something in my water buffering my PH.

I'm not going to have time to play with this again until the weekend but I want to repeat this experiment again. FYI I double checked the alkalinity in the tank this morning and it is actually a little higher than the tap maybe 17.5 - 18. The water from the tap changes color right at 17, when I do the water from the tank it starts to shift at 17 but doesn't fully change until the 18th drop is added. Could this be caused by the extra Phosphate added to the tank ?

Scott Hogsten


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## Bert H (Mar 2, 2004)

You mention your water comes through a softener. I am willing to wager that may be your answer. Why don't you run a test with a sample from the well before it reaches the softener and run the co2 and see what happens, and compare that to your current situatioin?


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## Roger Miller (Jun 19, 2004)

> quote:Originally posted by shalu:
> Simple question about your controller: is the ph probe close to the reator output? What is the ph target of controller? When ph is at 7.5-7.6, does the solenoid stay on all the time?


It would be good to have answers the Shalu's questions.

Your water is buffered by KH. Some well water comes with organic buffers but those usually force the pH down rather than holding it up. The phosphate in your tank would have to be very high (10's of ppm) to have a big buffering effect. Water softeners don't usually add buffers. All-in-all, you might have a non-carbonate buffer in the water but I don't see any reason to believe that is true.

Your test is a little confusing, mostly because I don't understand your setup. You took the controller out of the tank and the pH dropped. That means to me that the controller might have been keeping it from dropping, but that's only one of a couple different possible explanations.

Can you describe your CO2 setup, and how you changed things for the test? For instance, when running two reactors I assume both lines are controlled by the one CO2 controller solenoid valve. Do you have a needle valves on both lines downstream from the solenoid? Did you adjust the distribution of CO2 between your tank and the test bucket after you set up the test?

I can imagine all sorts of wild problems if you were running CO2 into both the tank and the bucket from the same controller while the controller probe was in the bucket.

Have you considered the possibility of stray current in your tank? Is it grounded? Power heads can be a source of stray current. You might try switching out the powerhead from your first reactor with the powerhead from the reactor that you had in the bucket.

Roger Miller


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## shogsten (Mar 17, 2005)

I did a lot of testing this weekend and something in my well water is causing some kind of bufferring effect. I pulled two five gallon buckets of water out of my tank and I took two five gallon buckets from the tap. I used a couple of powerheads to stir up the water and free any C02 in the water. If I put the reactor into the tank water (1 week old, PH 8.2 after 12 hours of agitation) and let it run the PH drops rapidily and within the hour to PH 6.8. If I do the same with tap water the PH 8.4 drops rapidly to ph 7.6, slowly goes to 7.2, sits at 7.2 then goes down to 6.8. this took around 90 minutes on both buckets of tap water. 

Now that I understand that I have this effect, I'm modifying my water change protocol to help deal with it. I have always done 50-75% weekly water changes usually closer to 75%. I'm going to switch and start doing 25-30% water changes twice a week. I'll probably vacuum on one change and just pull out water on the other. This should decrease the time that it takes me to get through the bufferring effect and I should be able to maintain a more stable PH and C02 level. I did the first of these changes around 1:00 yesterday, I did a 25% water change and turned on both reactors. This worked much better, by 6:30 pm I had the PH stable at 7.1.

To answer some of the other questions. 
1. Using well water not through the softener is not an option. The well has such a high iron content that unless I want everything a nice orange/red color I leave it alone. 
2. For the quick tests I did during the week leave one reactor running in the tank and one in the bucket. This probably did cause a bit of an imbalance so for my weekend experiments I installed a needle valve on both lines and turned off the needle to the tank.
3. Once I get the PH down in the tank I can easily control it with one of the reactors. It is even stable with the lights on. 
4. My setup is 20lb tank, fully open valve (I never ever run a tank with a partially open valve, that's just asking for problems), to a regulator, then to a selenoid controlled by the PH controller, then to the reactors. I have a bubble counter but I have started counting bubbles at the reactor. For the experiments I put a couple of needle valves in line to let me shut off the flow to one of the reactors. Note: the PH Controller agrees with two other PH test kits so it appears to be accurate. This was the first thing I questioned. 
5. The reactors themselves, One has a 200 gph powerhead (I think actually more like 100 gph), the other has a Rio 600 pump (200 gph). They are two inch white PVC with a short section of clear tube at the bottom (I did this so I can see the actual bubble rate at the reactors.)The total length of the reactors is 16 inches. The pumps inject from the side of the reactor chamber, near the top, at a slight angle to create some swirl. 
6. The reactors appear to be working well, I see a few very fine almost invisible bubbles coming from the reactor with the Rio 600. I don't see any coming from the the 200 gph powerhead one. The do build up an air bubble during lights on but I added a small hole (3/64") to allow the air to escape. I'm sure I lose a little C02 because of that but it only lets out any air late in the day, The rest of the time there is a slight flow of water out of it (plugging it made no difference).
7. The controller seems to be working well, the bubble rates stay constant (at the reactors) and during lights on the selenoid stays open most of the time, It will trip off every once and a while and stay off for a few minutes. 
8. I tried bubbling into my canister but I could not drop the PH below 7.4 and it was very unstable. Besides putting air into a liquid pump is just a bad idea. I've seen the results of captivation on a large oil pipeline pump.

Scott


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## Roger Miller (Jun 19, 2004)

Where does the pH probe go during your tests?



> quote:8. I tried bubbling into my canister but I could not drop the PH below 7.4 and it was very unstable. Besides putting air into a liquid pump is just a bad idea. I've seen the results of captivation on a large oil pipeline pump.


For what it's worth, cavitation in a pump is a different effect from having gas in the water. I saw impeller damage from cavitation in my irrigation pump. I've also fed CO2 through aquarium pumps for years now and have never seen anything like cavitation damage. For that matter, I've never seen any kind of impeller damage at all due to injecting CO2 into any aquarium pump.

Roger Miller


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## imported_shalu (Feb 13, 2004)

> quote:Originally posted by shog:
> It will trip off every once and a while and stay off for a few minutes.
> 
> Scott


It should NEVER happen unless the PH already reaches the target. And it should stay off for longer than a few minutes because ph will rise slowly to trigger the ph controller again, takes much longer than a few minutes.


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