# pH: 7.0 -> 6.6 daily?



## lauraleellbp (Feb 3, 2008)

Yes, that's a _*very*_ dramatic pH swing for fish. You need some more buffering in your tank- what are your kH and gH?

I would not recommend discus with that type of swing.


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## willbldrco (Mar 24, 2007)

Thanks for confirming my fears, lauraleellbp. It's odd: Since I dropped to twice weekly water changes (down from every other day with 50% tap and 50% RO), my KH has been in the 7-9 range. I typically like to see it at 4-5, but with these pH swings, I'm wondering if I should bother... GH is at about 8-9.

Will


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## BiscuitSlayer (Apr 1, 2005)

Based on my calculations from this page:

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

Your CO2 is ranging from 52.75 ppm to 67.821ppm which is a fairly high.

Based on your kh, you should be hitting a PH of around 6.8 .


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## BiscuitSlayer (Apr 1, 2005)

GH is irrelevant with regards to CO2 injection.


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## BiscuitSlayer (Apr 1, 2005)

My PH swings from 7.0 (right before lights on) to 6.6 (right before lights off), but my kh is 5. That puts me at 37.678 ppm of CO2 which is what my tank has been running at for about 6 months. Haven't had a single fish die, and alage issues are minimal.


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## NeverEndingNinja (Jan 4, 2008)

I'm of the belief that pH swings induced by co2 injection do not matter. It is not the change in pH, but the change in TDS(which is indicated by pH) that affects fish the most. A change in TDS can cause osmotic shock, where the fish can not regulate the fluid flowing through their body properly. This can cause a lot of stress, and potentially death.

Thats as best I can recall the discussion I read. A lot of peoples pH swings from >7 to <6.6 daily due to CO2 injection, with no ill affects on their fish. I even read of someones tank going from I believe >8 to <6.8 in a matter of minutes with no harm to their fish. I want to say it was Left C, but I can't speak for him. Perhaps he will chime in, however.


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## crazy loaches (Sep 29, 2006)

I'd wager to say the a larger swing due to CO2 is probably better, it indicates you have good gas exchange and means your running much lower co2 levels at night and most likely keeping o2 as high as possible.


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## SheriffBooth (Jan 25, 2008)

Yeah, Rex Grigg says ph swings from CO2 injection are normal and do not affect the fish the way a swing caused by an acid or base additive would. I wouldn't worry about it too much.


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## territhemayor (Aug 12, 2007)

I don't use a timer for my soleniod to turn off my CO2, I use a PH controller. This allows for my PH, even when the lights are off, to stay at whatever level I tell them to (6.5ish)
If the ph goes below that becuase of excess co2, it shuts off and the ph gets back to 6.6 or whatever, then the c02 turns back on again and so on. 
I find it alot better becuase I can keep the optimal amount of c02 in my tank at all times and I don't get the swing.


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## crazy loaches (Sep 29, 2006)

IMO I'd be shutting that controller down at night.


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## willbldrco (Mar 24, 2007)

BiscuitSlayer said:


> Based on my calculations from this page:
> 
> http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm
> 
> ...


Yes, and in fact, my KH measures even up to 9-10 occasionally with this new water change regime. That would be killing levels for my fish (who seem quite happy). I think my KH tests (have two API bottles which give the same result) are bogus. I recently got a drop checker and it's green with the tank measuring at pH 6.6. If that pH reading is accurate and if my drop checker fluid is a true 4dKH standard, I *think* that means my tank is at 4KH. Can anyone who knows drop checkers confirm?
Regards,

Will


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## crazy loaches (Sep 29, 2006)

People still dont get that they cant use the chart accurately to gauge CO2 levels in a tank, despite this being common knowledge for the last couple years (c'mon biscuit you've been here longer than I have :wink . The chart only works when co2 is the only acid and bicarb is the only base. It is possible for some that it may be close, but by no means is a good idea to assume these will be accurate for most. That is the reason we use a DC. In a DC we have a controlled environment with distilled/de ionized water in which the only base is bicarb (baking soda) and the only acid is CO2 diffused from the tank water into the air in the drop checker. There is no relation between anything within the DC and tank water other than CO2 levels (no correlation to pH, KH, etc).

Will, you seem unsure of the KH in your drop checker. Did you specifically purchase 4* fluid or make it yourself? Or are you just using tap water or something? For a reasonable amount of accuracy you need to make a fluid with at least 1/2 point accuracy or better yet buy some.


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## BiscuitSlayer (Apr 1, 2005)

crazy loaches said:


> People still dont get that they cant use the chart accurately to gauge CO2 levels in a tank, despite this being common knowledge for the last couple years (c'mon biscuit you've been here longer than I have :wink .


I didn't use a chart. I used a calculator. I did forget to mention that my tank water's PH right before the CO2 kicks on is 7.0 . I think it is pretty safe to say that I am getting accurate numbers.

Tell me I'm wrong?

I would think it is pretty safe to say that the numbers I provided for Willbrdco are fairly accurate as well based on the numbers he provided. His PH started at 7.0 as well. Assuming that his kh reading is accurate of course.

I think drop checkers are cool and everything, but I don't think they are as necessary as people say they are. I agree with you that it is a controled environment, but if you know the starting PH prior to the CO2 starting up then you have a point of refrence for your reading towards the end of the day.


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## willbldrco (Mar 24, 2007)

> Will, you seem unsure of the KH in your drop checker. Did you specifically purchase 4* fluid or make it yourself? Or are you just using tap water or something? For a reasonable amount of accuracy you need to make a fluid with at least 1/2 point accuracy or better yet buy some.


I used VaughnH's recipe for a 4KH standard using RO and month-old baking soda, but, regardless, mathematically, I could not reproduce his calculations (my math shows his recipe should produce a 8dHK solution). Experimentally, with API, I get a 7dKH reading so that's two strikes against my faith in VaughnH's recipe (it's closer to my calculated value).

Don't get me wrong: I would not bet a dime that I'm right. If API is correct, my fish should be belly up (ok, I'm using that outdated CO2 table again!). I'd just like to know where the error lie. I've checked and rechecked the math. I've ordered some 4dKH standard.  I'll check it against my homemade swill when it comes in.

But what about my drop checker question:



> Recently got a drop checker and it's green with the tank measuring at pH 6.6. If that pH reading is accurate and if my drop checker fluid is a true 4dKH standard, I *think* that means my tank is at 4KH. Can anyone who knows drop checkers confirm?


In other words, at a "green" drop checker color, with a known pH of 6.6 for the tank water, does it follow that the tank water is at 4 KH?
Curious,

Will


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## BSS (Sep 24, 2004)

willbldrco said:


> But what about my drop checker question:
> 
> 
> 
> ...


In my experience, no. Math and formulas are great, but they also assume an ideal world/environment. That ain't life, IMO. Since setting up my tank several years ago, my KH has always been in the 7-8 range. Yet by keeping my pH in the range that would suggest 30+ ppm range, I continue to get thriving BBA. As the collective knowledge of the forums would have me believe, that means my CO2 levels are very likely below 30 ppm. I too finally just got around to setting up my drop checker. I home made a 4.5 dKH solution (using my single, aging KH kit...so the accuracy is questionable), setting my SMS controller to give me a pH around 6.5, gives me a yellow-greenish color to my drop checker. So, based on that I'm thinking my CO2 levels are around 40-50.

I don't think what I see indicated in the drop checked has any real bearing on my KH levels. Based on year's of measurements (granted with cheesy test kits), I still believe my KH is 7-8. It just makes me not want to rely on the "tried-and-true" CO2-KH-PH charts.

That's how I choose to understand it,
Brian.


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## MarkMc (Apr 27, 2007)

My 2 cents based on what I'm seeing in my 55g. Using a automated co2 system set at 6.8 with KH of 6/6.5. Decided to put my solenoid on a timer to reduce co2 usage at night (the controller is on so I can monitor ph at night). Many posters here have said that they do this and have had no problems so I tried it. No problems at all. I'm seeing a day to night swing of 6.8 to 7.5. The plants are growing great-algae is in retreat and the fish look spectacular.


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## willbldrco (Mar 24, 2007)

MarkMc said:


> I'm seeing a day to night swing of 6.8 to 7.5. The plants are growing great-algae is in retreat and the fish look spectacular.


Thanks for that info! I feel much better. 

I don't use a pH meter, but I have started using a drop checker and it is certainly aqua in the morning and clearly green about 5-6 hours later. With this new CO2 blast (and also a somewhat surprising accompanying tank thirst for phosphate and potassium), the pearling has exploded. Most plants are doing very well.

Will


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## BiscuitSlayer (Apr 1, 2005)

willbldrco - 

Have you changed your bps rate or do you have it the same as where it was at when you started this thread?


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## willbldrco (Mar 24, 2007)

BiscuitSlayer said:


> willbldrco -
> 
> Have you changed your bps rate or do you have it the same as where it was at when you started this thread?


This thread was started just after I increased the rate from 1.2 bps to ??? (the bubbles flow too fast to get a good count). If I had to guess, I'd say it's now near 3.5 bubbles/sec.

Basically, my pH was at 6.8 and, to combat BBA, it was suggested that I get a drop checker and up the CO2 injection until my pH was 6.6 and the drop checker showed green. My CO2 injection rate, drop checker color, and pH have been constant since.

My KH has increased (probably due to cutting back my water changes to 50% weekly which started at the same time as the CO2 bps rate change), but I'm not sure how much as I don't trust my KH test kit.

I think 3.5 bps is alot for a 55g so I'm going to replace my inefficient injection method of simply connecting my CO2 tube to a powerhead's air intake to Rex's well-received homemade reactor.

Will


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## MarkMc (Apr 27, 2007)

I'm injecting that much or more in my 55g. I do have a trickle filter though and mh lighting so it's definitely not too much. Why don't you trust your KH kit? I've never seen any comments about inaccuracy in those kits.


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## willbldrco (Mar 24, 2007)

Hey MarkMc,



MarkMc said:


> I'm injecting that much or more in my 55g. I do have a trickle filter though and mh lighting so it's definitely not too much. Why don't you trust your KH kit? I've never seen any comments about inaccuracy in those kits.


I don't trust my (2 identical API) kits for two reasons:


Both kits give a reading of 7dKH for the 4dKH standard recipe by VaughnH (although I question his math/chemistry - I get an 8dKH standard from the recipe when I perform the calculations)

Both kits have given readings of 9 and 10 dKH with the pH at 6.6. Fish should be dead at that point, but mine don't even come to the surface to gulp.

Something is amiss with those kits. I need to order a 4dKH standard so I can be sure, tho.
Regards,

Will


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