Ph solenoid CO2 night shut off and SWINGS
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Old 09-04-2009, 04:40 PM   #1
Planteater
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Ph solenoid CO2 night shut off and SWINGS


Hi,

I just set up a gla co2 regulator system and feel i wasted money on the solenoid valve. i dont get the point of it, if you have fish.

if you shut off the C02 at night doesnt that make your ph go up? and then it goes down again in the day. Is that ph swing ok for fish such as thin-skinned fish or discus?

I dont want to add a ph controller to my costs, so i am wondering why the hell i got a solenoid and what you guys do about ph swings in night shut off. also i hate the idea of leaving that super hot solenoid on 24/7, seems like a fire hazaard.

any advice is much welcome

thanks,
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Old 09-04-2009, 05:08 PM   #2
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Well during the day CO2 is consumed by the plants and you adjust your bps to give you consistent ~30ppm of CO2. At night, no Co2 is consumed by the plants so CO2 levels rise and depending on the rate your fish could be dead by morning. A solenoid turns off the CO2 at night so that you can properly supply CO2 during the day without gassing the fish at night. Without a solenoid you either have to turn it on/off manually or adjust your bps low enough that CO2 levels dont rise to lethal levels by morning. The latter option usually means during the day you will have less than optimal ppm of CO2.

And the solenoids are designed to run even if quite hot, I have read some are designed to work up to 140F.

The pH swing is harmless to fish(unless you are going from say 2.5 to 12) since the pH swing of proper CO2 levels vs. no CO2 is only about 1-2 pH. Fish aren't bothered by this.

The common way of using the solenoid is to have it turn on about 1-2 hours before lights on and then off at lights off. A pH controller isn't required for fish health or proper plant growth.
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Old 09-04-2009, 07:07 PM   #3
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I was thinking to manually adjust the needle valve at night to not overdose the CO2 but not cause the ph swing. my swing last night was from about 6.4-7.4. when the C02 came on again, my thin skinned fish were soon stressed.

of course i could take them out and live with a ph1 swing. or doing it manually i can keep ph stable and everyone's happy, but then the solenoid is useless then
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Old 09-04-2009, 07:12 PM   #4
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I keep mine on a timer like postal penguin mentioned. I have Apistos in my tank and they are not stressed. If the fish are stress, then you are probably pushing too much co2. With fish that like such soft water you have to be a little more careful since your normally low on some of the buffering agents.
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Old 09-04-2009, 07:16 PM   #5
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I'm not one to jump of a bridge if all my friends are doing, but I would guesstimate that 90% of the people here who use pressurized CO2 use a timer and a solenoid. Just use it, try it out, and then see what you think. Considering how popular they are, I think you should give it a shot.

If anybody else here doesn't use one, please post your opinion on the downside to them. I'd be curious to hear it.
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Old 09-04-2009, 07:42 PM   #6
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Manually adjusting the NV twice a day isn't something I'd look forward to.

I'm pretty good at understanding the how's and why's of aquatic chemistry but I just can't wrap my head around why I shouldn't be concerned with CO2 induced changes. So in this case I just had to ignore what I've always thought of pH changes and how fish react.

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Old 09-04-2009, 11:48 PM   #7
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i dont mind manually adjusting it, while the ph swing bothers me. however i can admit that like GTR it might just be a mental habit. why wouldnt co2 induced ph swings matter?

i will continue to use the soleniod and timer but i had not thought through the consequences of that. My discus seem unphased, but i have corys, otos, siamese ae, and clown loaches that dont like it when the CO2 comes on suddenly.

or at least thats what they told me

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Old 09-04-2009, 11:55 PM   #8
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I read a post on this forum that said that because the pH doesn't affect the hardness of the water, it doesn't bother the fish. I don't know if that's actually true or not. My pH drops from ~7.4 to ~6.4 and the fish seem fine.
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Old 09-05-2009, 12:02 AM   #9
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All depends a bit, like how much CO2 and how much current -> CO2 loss and how many and what plants and such, but...

When the CO2 turns on, it's not like the pH plummets all of a sudden. And when it turns off at night, it's not like it jumps up all of a sudden.

So, without a pH controller, you can pick your poison. Use a timer, turn off CO2 with lights off: pH theoretically goes up, but it might not be that much. Run 24/7, at night plants don't use any, pH might go down further.

Now that's just a simplified explanation. The percentage of CO2 that's used by plants is actually relatively small. What's more important, at night plants don't photosynthesize, and the O2 levels go down. That's really what makes 'em gulp... and high CO2 levels might just aggravate that.

Using CO2 a timer saves CO2, doesn't hurt plants, and makes fish happy. Forget about the pH jumps. If your fish react badly to the CO2 coming on it's not because it is on a timer, but because you are overdosing. I guess.
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Old 09-05-2009, 03:34 AM   #10
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Some people use timers on their pH controllers so that they can cut the CO2 off at night. Then when it comes on, it adjusts to the set pH amount and then it keeps the pH stable during the day. The timer can be placed between the power cord for the solenoid and the electrical control unit that sends the on/off power to the solenoid.
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Old 09-05-2009, 03:57 AM   #11
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Quote:
Originally Posted by FSM View Post
I read a post on this forum that said that because the pH doesn't affect the hardness of the water, it doesn't bother the fish. I don't know if that's actually true or not. My pH drops from ~7.4 to ~6.4 and the fish seem fine.
CO2 does not affect the TDS (total dissolved solid) content of the water; as a result, fish are not affected by the pH swing as a result of injecting CO2.

Compare this with (say) chemical buffers where you are adding various salts to increase/decrease the pH. This will increase the TDS in the water, thus stressing the fish (osmotically).
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Old 09-05-2009, 09:12 AM   #12
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I think pH swings are overrated, my pH can sway between 5.8 to 6.7 with no problems. There is no good reason to dose CO2 after the lights turn off; it's not useful to either the fish or the plants.
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Old 09-05-2009, 03:01 PM   #13
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thanks! thats all pretty convincing.
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Old 09-05-2009, 06:09 PM   #14
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Quote:
CO2 does not affect the TDS (total dissolved solid) content of the water; as a result, fish are not affected by the pH swing as a result of injecting CO2.
WHAT? no, no, no! Carbonic acid lowers the pH, more c02 you add, the lower the pH goes. It is how fast the drop is that kills fish. Its called pH shock. It depends also on the fish and how sensitive they are to it. Ph swings over a period of several hours are gradual enough not to bother most fish.

If any one here has ever been into soft water fish, dwarf cichlids and the like and picked up fish at a club auction, you know you have to acclimate the fish to the water in your tank very very carefully. You very slowly add small amounts of your tank water into the bag of water with the fish over a period of an hour or more. This prevents the fish from going into pH or temperature shock. Its the same thing with C02. You raise the level of C02 slowly over a period of several hours. Co2 tank dump syndrome is when your C02 tank is near empty and it dumps the entire remaining contents into your aquarium. Your fish die from pH shock before they die from C02 poisoning

If your water has no buffers at all, virtually no KH, then your normal pH swings from morning to night will be much bigger and irradic
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Old 09-05-2009, 08:14 PM   #15
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Quote:
Originally Posted by Robert H View Post
WHAT? no, no, no! Carbonic acid lowers the pH, more c02 you add, the lower the pH goes. It is how fast the drop is that kills fish. Its called pH shock. It depends also on the fish and how sensitive they are to it. Ph swings over a period of several hours are gradual enough not to bother most fish.

If any one here has ever been into soft water fish, dwarf cichlids and the like and picked up fish at a club auction, you know you have to acclimate the fish to the water in your tank very very carefully. You very slowly add small amounts of your tank water into the bag of water with the fish over a period of an hour or more. This prevents the fish from going into pH or temperature shock. Its the same thing with C02. You raise the level of C02 slowly over a period of several hours. Co2 tank dump syndrome is when your C02 tank is near empty and it dumps the entire remaining contents into your aquarium. Your fish die from pH shock before they die from C02 poisoning

If your water has no buffers at all, virtually no KH, then your normal pH swings from morning to night will be much bigger and irradic
There is nothing like a good debate to keep the blood flowing!

The problem with your position, Robert, is that so many of us do 50% and greater water changes weekly, dumping in fresh tap water, with Prime added, but with whatever pH that water has. And, most tap water has a high pH. That very suddenly raises the tank pH quite a bit. But, the fish thrive on such changes. So, pH shock is very likely to be a myth.

Also, adding CO2 by any means available to us, does not rapidly drop the pH. We just can't get CO2 dissolved into the water that fast. The pH change occurs gradually, most likely over a 2 hour or so period. That is not a sudden pH shock.

Last, when we condition our fish, just purchased from the LFS, it isn't the pH change that we are protecting against, but the other water parameters changing rapidly. LFS may have much higher KH or GH than our tank has, or our tank may have much more tannins than the LFS has. It is very likely that those are the sudden changes we have to guard against.

Your turn!
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