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Old 05-19-2005, 10:12 PM   #1 (permalink)
 
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Default Harmful Ph Swing?

Please correct me if I am wrong, but the way I understand the effect of CO2 on Ph is that even though the CO2 lowers the Ph reading in the tank, it will have no effect on the fish. That is, what effects the fish are the Gh and Kh and that the CO2 simply spoofs a temporary Ph reading until it dissipates.

That being said, I want to follow Tom Barr's advice and crank CO2 during lights on and shut it off during the night. This will cause my Ph reading to fluctuatae between 8.1 and 7.2. I keep Tanganyikan Cichlids that like a high Ph (assumed related to Kh and Gh), but can I really induce this level of extreme flutuation without consequences.

I have cranked down the controller to as low as 7.5 and since doing so have lost two Cyprochromis Leptosoma and a Neo. Gracalis. All other water parameters are in line; no amonia, no nitrites, frequent water changes etc. Could it just be coincidence these fish died? All the fish look and act fine.

So, can I fluctuate Ph by .9 daily through CO2 injection without harming the fish assuming all other parameters are fine and there are no diseases?

Thanks to all....
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Old 05-20-2005, 01:29 AM   #2 (permalink)
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I have 0.7(6.6-7.3) daily ph swing in my discus tank, all the fish say who cares.

Is ph 8.1 assuming little CO2 left? Actually, I found I have about 10ppm CO2 before the next cycle, so your swing might be smaller than you think.

How long before the fish died you added new fish? Hard to believe it is related to CO2, your CO2 level is not that high.

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Old 05-20-2005, 02:37 AM   #3 (permalink)
 
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It is not the magnitude of the pH fluctuation, rather the temporal duration in which the fluctuations occur which is important.

I ran into one problem and noticed that the Yamoto’s were not happy; my mortality rate seemed to be one a day. I would come home the CO2 had been on for a while and as usual, there was this one reddish Yamoto doing laps of the tank, it might go pale, but inevitably it would be the next Yamoto that would die. Now this went on for days, a death a day. The plants were growing like crazy, which was good, Guppies were happy.

I Noticed that my external reactor was expelling some bubbles, a sign that some of the CO2 was not getting dissolved and getting wasted. One adjustment was made, changed the CO2 from 3bps to 2 bps. That evening it was noticed that it took longer for my pH come back down. Well the next day by accident I saw for the first time some normal behaviour and no deaths, with no problems since then.

This was an important event as I am new to the hobby. Unknown problem, effect observed and solution found. What I like about Tom Barr’s advice is not to tinker around with too many variables, so that cause and effect are easily seen. If you tinker with too many variables you cannot easily differentiate between cause [action] and effect [outcome] with any degree of confidence especially if there is temporal bridge between the two and the observable change is gradual. The hard part is sticking to a course of action until the effect is seen; changing one variable at a time avoids complexity.

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Old 05-20-2005, 04:54 AM   #4 (permalink)
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What is the kH of your water? Unless you have extremely soft water, your pH will not vary as you think (8.1-7.2). My pH varies around 0.3 units at most, and all fish and shrimp are fine. 3 of my 4 tanks run CO2 24/7, the third is on a solenoid shut off when lights go off and I have no pH issues in any of them. HTH.
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Old 05-20-2005, 08:45 AM   #5 (permalink)
 
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Thanks to all fo rthe responses!

Bert: My KH is 10 out of the tap and I buffer it up with baking soda to 16. My Ph is 8.1 out of the tap and I allow the CO2 injection (via the controller) to push it down to 7.5. That gives me roughly 15 ppm of CO2. The reason I am asking about the swing is if I set the controller to 7.3, I get 24 ppm of CO2 and if I can go as low as a Ph of 7.1, I get 30 ppm CO2.

Currently I run the CO2 24X7. I'd like to have it run only during the photo period AND I'd like to add more. So, really my questions are:

A) Can I drop the lower limit of Ph to 7.2 without harming the fish?
B) If I do that and run the CO2 only during the day, would a swing from my tap Ph of 8.1 to 7.2 harm the fish?

Other information:

My tank is medium planted, but will be heavy when the plants grow out
My lighting is 396 watts on a 150 gallon tank
I am fertilizing using EI, but my uptake is not very high due to low CO2.
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Old 05-20-2005, 08:50 AM   #6 (permalink)
 
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Rupert:

I may have the same issue going. I have an external reactor and I notice it spitting out CO2 bubbles also. I am injecting 3-4 bubbles per secon too. I'll try to crank it down some especially since I am running it 24X7.

Thanks! I truly appreciate the help. I am slowiy unlearning all the habits of a Tanganyikan cichlid fish only keeper and adaptingto planted aquariums. (got the bug bad). There are many contradictory characteristics I have to gain the confidence to change.

Most folks tell me to just change the fish I keep, but I'd really like to try to pull this off.
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Old 05-20-2005, 11:11 AM   #7 (permalink)
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My KH is 10 out of the tap and I buffer it up with baking soda to 16.
Why are you doing this??? I don't understand what purpose this would serve for you. Is it a fish requirement? The only time you need to increase your kh is if you're below 3 because then you would have problems with kh/ph and CO2. My kh is 9.5, with the CO2 addition, I drop it to about 6.9, which gives me around 35ppm CO2. As I said, all inhabitants are happy. Remember if you're going to ph your tap water to let it sit for a while first.
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Old 05-20-2005, 11:25 AM   #8 (permalink)
 
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Bert:

Indirectly it is a fish requirement. Tanganyikan cichlids natural environment is hard water 10+ dKH and a high Ph in the 8.1 - 9.0 range. I am trying to add as much CO2 as possible for my plants while keeping the Ph as high as possible for my fish.

By adding baking soda to drive the KH up to 16 (which the fish enjoy) I can add more CO2 without totally crashing Ph. I've proven to myself the fish can handle a ph of 7.5, but at a ph of 7.5 and a KH of 16, I can only get 15 ppm of CO2. If I can prove to myself the fish can handle a ph of 7.2, then with a KH of 16, I will be adding almost 30 ppm of CO2. (See the CO2 calc here: http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm )

I can also raise the KH through further buffering with baking soda and attain a higher CO2 level that way, but you don't get as much movement upwards in CO2 absorption by adding KH as you do by allowing Ph to fall.
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Old 05-20-2005, 12:51 PM   #9 (permalink)
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I see. I've never kept cichlids. Good luck, keep us posted with the progress.
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Old 05-20-2005, 01:50 PM   #10 (permalink)
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In theory, your fish should be fine at the lower pH level. i am keeping/spawning some Lake T. shell dwellers in water that is pretty soft by your standards. kH 3-5 and Gh less than 9. They have spawned twice in less than 2 months and the fry seem to be growing and developing just fine. Unless you fish are wild caught, any tank raised fish have probably been raised for a great many generations in un-natural conditions. Taking the pH level down slowly, over a day or so, is hte safest although probably unnecessary.

I am a plant dork, not a fish dork though so I speak only from limited experience HTH, and welcome to APC!
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