# Do you use an airstone at night?



## colinthebassist (Nov 30, 2007)

If your going pressurized you can turn off the CO2 at night eliminating the need for an air stone. Only with DIY is it a good idea.


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## Darkblade48 (Jan 4, 2008)

The main reason people run an airstone at night is to prevent too much CO2 buildup. By agitating the surface of the water, it promotes exchange of gases in the water with the atmosphere; since you're injecting CO2 into the water, it will be at a higher concentration in the water than atmospherically, so it will degas out of the water.

There aren't really any pros and cons, in my opinion. As mentioned, only with DIY might it be worthwhile, since you can't really control the rate at which CO2 is being produced.


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## 9am53 (Jan 23, 2008)

I have the outlet from my fluval quite low in the water, so there is very little movement at the surface of the water. if I was to turn the CO2 off at night, would the fish and plants not consume most of the dissolved O2 before morning? Would the airstone not also help in allowing more O2 to dissolve?

And regarding the pH swing overnight if CO2 is turned off, is it wise to add baking soda to increase kH and reduce the swing?


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## mott (Nov 23, 2006)

I am a big advocate of having a little bit of a ripple at the surface.
Surface scum will build fast with no movement thus blocking the light and an ugly top of the tank

I used to use an airstone but I now just point my spraybar to the top for a small ripple.
My co2 turns off at night, if you run your co2 24/7 you might want to turn the airstone on at night just for good mesures.
Good luck.


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## Naja002 (Oct 12, 2005)

mott said:


> I am a big advocate of having a little bit of a ripple at the surface.
> Surface scum will build fast with no movement thus blocking the light and an ugly top of the tank
> 
> I used to use an airstone but I now just point my spraybar to the top for a small ripple.
> ...


That's the ticket. Generally speaking, there's a "sweet spot" of surface movement that will not excessively outgas C02 and still allow sufficient 02--day and night. roud:


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## 9am53 (Jan 23, 2008)

not to hijack, but would ideally there be: 

i) a slow current around the tank, but nothing at the water surface directly above the filter outlet
ii) a slow current around the tank, + a slight little "cyclone" above the outlet
iii) a slow current, plus a little actual "ripple" above the outlet

And in the ideal case there would be enough O2 over night with no airstone?

thanks for the thread chaos theory!


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## mgamer20o0 (Mar 8, 2007)

i do not use a air stone and my co2 runs 24/7. if you dont want to take the risk turn it off at night.


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## 9am53 (Jan 23, 2008)

Darkblade48 said:


> The main reason people run an airstone at night is to prevent too much CO2 buildup.


Why do we want to avoid CO2 buildup? the CO2 building up is not displacing any O2 right? Dont we just want to avoid O2 starvation, hence running the CO2 over night is fine as long as there is some gas exchange going on to let O2 in?


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## Naja002 (Oct 12, 2005)

9am53 said:


> Why do we want to avoid CO2 buildup? the CO2 building up is not displacing any O2 right? Dont we just want to avoid O2 starvation, hence running the CO2 over night is fine as long as there is some gas exchange going on to let O2 in?


Correct--its not about C02 build-up--its about low 02. When photosynthesis is done ("at night") plants switch to *using *02, instead of releasing it. So, without adequate surface disturbance--02 may run low.





9am53 said:


> not to hijack, but would ideally there be:
> 
> i) a slow current around the tank, but nothing at the water surface directly above the filter outlet
> ii) a slow current around the tank, + a slight little "cyclone" above the outlet
> ...




Correct again. Its not about the current or current pattern--its about surface disturbance. An air pump/stone does not "add" 02 in the same sense that a ceramic diffuser adds C02. In other words, its not about "dissolution"--its about surface disturbance. An air pump/stone "disturbs" the surface of the water--via rising bubbles--creates the disturbance which allows the 02 gas to be absorbed by the surface water. Then the current spreads it around the tank.

You just need X-amount of rippling from a powerhead, canister, whatever. However, "X-amount" is determined through your trial and error.

Less is better, but you need enough to provide for the 02 exchange.....

roud:


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## 9am53 (Jan 23, 2008)

Naja002 said:


> You just need X-amount of rippling from a powerhead, canister, whatever. However, "X-amount" is determined through your trial and error.
> 
> Less is better, but you need enough to provide for the 02 exchange.....
> 
> roud:


So just to finish my hijacking, if in the morning I find my fish at the top looking like they are "drinking" air from outside the tank then they are O2 starved, and I need to add a bit more disturbance over night right? and regarding what I asked earlier (I truly apologize for the repeated selfish questions) is it bad to add buffer to reduce the pH swing if I do decide to save CO2 and turn it off at night? or is the swing not really a big deal.

Thanks, these have been bugging me for a while, and I'll shut up now :icon_eek:


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## imeridian (Jan 19, 2007)

I'm also a fan of surface movement, I have pretty good "ripple action" on my 75, might lose some CO2, but the benefits outweigh that in my opinion. So, no airstone at night, but I do cut the CO2 off with a solenoid.

There can be too much CO2 though, the fish would suffer from hypercarbia/hypercapnia and suffocate even though there was plenty of O2 available. I agree though that the problem is usually low O2.

--
9am53, don't worry about the pH swing, the fish can't tell. Regardless of your KH, you'd have a 1 point pH drop anyway (when adding 30ppm CO2), so all you'd be doing by adding extra buffer would be pushing up your baseline pH needlessly, potentially shocking the fish by increasing the TDS if done too rapidly.

You absolutely need to take action if your fish are gasping at the surface in the morning. Increasing surface agitation will likely make the fish much more comfortable.


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## 9am53 (Jan 23, 2008)

Thanks


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## chaos theory (Feb 16, 2008)

Thanks everyone for your advice and experiences!

I plan on getting a solenoid on my co2 tank so I can program it to turn off at night and my spraybar creates a small ripple in the surface of the water so I'll see how that goes and adjust from there if I need to.

Thanks again!


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## waterfaller1 (Jul 5, 2006)

How do you 'program a solenoid' to turn off your CO2? I thought I had to do it with the plug in a timer? Thanks for the info on the airstone, did a search and this thread came up first.:icon_smil


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## @[email protected] (Oct 24, 2007)

timers work for CO2, but i preffer ph controllers (they shut off the CO2 when the ph drops to a certian point and turn it back on at another point). i never heard of programing as solenoid valve though.

i use a powerhead at night (aimed at the surface). its less noisy then an airstone.


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## Church (Sep 14, 2004)

I use DIY CO2, and I never run an airstone. I read somewhere that adding an airstone at night would be counter-productive in the long run, because it will cause the pH to constantly swing.

I don't think DIY style causes too much CO2 to be produced in the first place, so the pH swings end up being more detrimental.

FWIW.


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## TheCryptKeeper (Mar 9, 2008)

I use an airstone at night.. it is one the same timer with my lunar lights. I feel that it doesn't hurt anything to have one going... so better safe imo than sorry.


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## TheCryptKeeper (Mar 9, 2008)

anytime you introduce co2 into a tank you are causing a ph swing. it is just how much of a swing and how quickly it happens that causes problems.


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## ColeMan (Mar 9, 2008)

yeah, you're right; if you're using a controller you can get within .03 of a desired target pH range, minimizing if not eliminating pH fluctuations...So by injecting CO2 in conjunction with a controller, you are actually maintaining a constant (or near constant) pH.


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## @[email protected] (Oct 24, 2007)

thats why i use them, i need the aireation at night otherwise my ph drops too low. i actually have such a high biomass that when everything is respiring at night, i have more CO2 in the tank then during the day.

i switched 2 words that completely changes the meaning of the post. thats the reason for editing.


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