co2 and ph
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co2 and ph

This is a discussion on co2 and ph within the Beginner Freshwater Aquarium forums, part of the Freshwater Fish and Aquariums category; --> I was always told that using CO2 in a tank SLIGHTLY lowered the ph, so I thought no problem, my ph is generally 6,8 ...

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Old 04-30-2009, 12:39 PM   #1
 
co2 and ph

I was always told that using CO2 in a tank SLIGHTLY lowered the ph, so I thought no problem, my ph is generally 6,8 and I have only soft water fishes, so I set up a small DIY co2 system in my 33g (basically a 1,5 liter ketchup bottle with sugary water and yeast, and a small tube leading to the canister filter intake). I set everything up and checked to make sure the intake wasn't sucking everything up, seems fine, I go to bed.

This morning I check the ph and it's down to 5,0!The bottle is slightly bombed so I know the intake is not sucking all the co2 out of it. Anyone can help me figuring this one out?
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Old 04-30-2009, 07:39 PM   #2
 
What does bombed mean ?
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Old 04-30-2009, 10:09 PM   #3
 
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What does bombed mean ?

Aw crap sorry I think I 'anglicized' a french word here. I meant curved, like if it was deformed by trapped gas
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Old 05-01-2009, 11:24 AM   #4
 
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Originally Posted by Freddiesbuns View Post
I was always told that using CO2 in a tank SLIGHTLY lowered the ph, so I thought no problem, my ph is generally 6,8 and I have only soft water fishes, so I set up a small DIY co2 system in my 33g (basically a 1,5 liter ketchup bottle with sugary water and yeast, and a small tube leading to the canister filter intake). I set everything up and checked to make sure the intake wasn't sucking everything up, seems fine, I go to bed.

This morning I check the ph and it's down to 5,0!The bottle is slightly bombed so I know the intake is not sucking all the co2 out of it. Anyone can help me figuring this one out?
Several things affect the pH of an aquarium, such as the fish load (number, size), plants (number, which ones as they grow differently), filtering system, gravel or rocks that have properties that increase hardness and pH, and the buffering capacity of the water. The hardness of your water will give a clue as to its buffering capabilities. Adding CO2 certainly lowers the pH, and at some point the buffering agent in the water will be exhausted and the pH will then suddenly drop because there is nothing to stop it when the buffering limit is reached.

I have read posts from those who use CO2 and most seem to shut it down at night. The reason is that plants utilize CO2 for photosynthesis and this can only occur during daylight. In darkness, the plants do not consume CO2 but continue to expel it the same as the fish. During darkness there is consequently a natural increase in CO2 in an aquarium, and the pH falls slightly. During the daylight when the plants utilize CO2, the pH rises a bit as the CO2 is taken up out of the water. A normal planted aquarium has a natural diurnal pH variation of approximately 2-5 decimal points, depending upon the number of plants and fish.

I have never used CO2 in my planted tanks as I have no need for it; the pH of my tap water is 6.8 and it is soft, and the type of plants I maintain grow very well with the nutrients and light balance in the tanks. My two tanks both fluctuate diurnally from 6.4 to 6.6, and as I do not inject CO2 this is completely natural. Continuing to drive CO2 into the tank at night will cause the pH to drop even more, obviously, and once the buffering capacity in the water is maxed it will plummet.
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Old 05-01-2009, 09:42 PM   #5
 
That I didn't know! It would explain why the ph is under 7 in this tank while it's been 7 to 7,5 in all the other tanks I have had (not to mention my tap water is 7).
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Old 05-02-2009, 09:48 AM   #6
 
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That I didn't know! It would explain why the ph is under 7 in this tank while it's been 7 to 7,5 in all the other tanks I have had (not to mention my tap water is 7).
I hope you do something to immediately correct this in the CO2 tank. Do not have it jumping around more than a few decimal points within any 24 hour period; a decimal point is 6.5 to 6.6 for example. If the pH changes more than a few decimal points within 24 hours it is extremely stressful on the fish and before long they will probably be getting diseased if not dying.

Each degree on the pH scale is a factor of ten, so a pH of 6 is ten times more acidic that a pH of 7, and a ph of 5 is 100 times more acidic that a pH of 7, etc. The reason this is so disastrous to a fish has to do with the complex chain of internal reactions that keep the pH of a fish's blood steady, its tissues fed, and its immune system functioning. A change in pH affects how hard a fish's body must work to maintain this physiological equilibrium. The fish's cells must have water, and as fish cannot drink they absorb water through their cells (osmosis), and the internal pH must be regulated to equal the pH of the water they are absorbing, which is the pH in the tank. When the tank pH changes, the fishes' bodies must work to maintain this equilibrium, and the greater the change in pH the harder they must work. This leads to stress, and the fish is more susceptible to disease, and eventually the strain may kill it outright. A stable pH is critical to a healthy aquarium.

Interesting that you have another tank where the pH 7 of the tap water rises to 7.5. Normally, pH falls slightly as the biological system operates in an aquarium. You must have something in the tank making the pH rise, such as dolomite, limestone or coral gravel or rocks. That's OK if you want it higher, as for African rift lake cichlids or livebearers. But I wuldn't do this for fish that prefer acidic water. Same reason as the pH issue above, a pH outside a fish's preferred range means stress.

Shifts in pH can also occur if you have a water softener in your home, as these often use various chemicals to adjust hardness and thus pH and the buffering capacity of water can alter in the aquarium.
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Old 05-02-2009, 01:26 PM   #7
 
Right now I've added baking soda and it put my ph up to about 6,8, but it must be temporary. I've tested my gh/kh and both are fine, gh=60 and kh=20. But I do remember my kh used to be higher than 20.
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Old 05-02-2009, 07:27 PM   #8
 
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Right now I've added baking soda and it put my ph up to about 6,8, but it must be temporary. I've tested my gh/kh and both are fine, gh=60 and kh=20. But I do remember my kh used to be higher than 20.
Monitor the pH. I would turn down the CO2 or shut it off completely until this is figured out. If you continue running it I suspect the pH will keep falling once the buffering capacity is gone.
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Old 05-02-2009, 08:16 PM   #9
 
Byron, thanks for the info.


Now Im just going to hook the CO2 DIY I made into the light timer, Its a dual time timer so do you think I should only maybe give it CO2 half the time of the light?

My PH as of today is at 8.6, I put in the PH nuetralizer from SeaChem in this afternoon and it is down to around 8.0, I am going planted I dont have any yet because I gotta add more sand and get the food for the plants, what else in the water parameters should I look for? My CO2 set up is DIY my container is a 1 gallon jug, I did however add an in-line water seperator to catch the yeast muck so the check valve doesnt get clogged up and its much easier clean-up. I am using a wood chop stick for a difuser however I am placing a food and plant order and will get it then if needed.

What rate should the bubbles be? any certain 1 gallon mixtures for the yeast,sugar and b. soda?

Thanks


Dont mean to hijack just didnt want to make a new thread for the same and new questions.
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Old 05-02-2009, 10:39 PM   #10
 
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Monitor the pH. I would turn down the CO2 or shut it off completely until this is figured out. If you continue running it I suspect the pH will keep falling once the buffering capacity is gone.
The co2 have been turned off for 3 days already. But once it was turned off, I saw no change on the ph until I added baking soda. That's what I find strange.
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