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Night shut-off for DIY CO2


15 Feb 2008
Would it be feasible to fit a solenoid to a DIY CO2 setup?

Obviously not to the tank feed, because then the bottle might explode :wideyed: But if you had a second tube coming from the bottle with the valve on it, it could be 'off' in the day and 'on' at night.

This would allow CO2 to escape into the room air at night, removing the pressure necessary to force it down through the water column and through the diffuser. A bubble counter could be fitted to the outlet to prevent air getting back into the yeast bottle.

More importantly, would the benefits of night shut-off be worth the bother and cost of setting this up? I am keeping tiny rasboras in a 4g setup, and am worried about suffocating them.

Any thoughts would be welcome,


ps - can someone please tell me how to insert a picture into the message? Cant figure it out :D

Ed Seeley

3 Jul 2007
There are a number of ways of doing things here;
run CO2 24/7 and make sure there is plenty of surface agitation to keep O2 levels high.
run CO2 24/7 and have an air pump on a timer to come on at night to boost surface agitation and Oxygen exchange.
turn the CO2 off at night and then have it coming back on half an hour or so before lights on.

Personally, when running pressurised CO2 at 30ppm I turn the CO2 off at night or I'm sure the fish would have problems if I kept injecting CO2 all through the night.

However when running DIY CO2 I left it running as I never got the CO2 up to 30ppm. It used to run at around 15-22.5ppm CO2. That tank had a HOB filter which meant there was plenty of surface agitiation at all times. I think you'll be fine running it constantly as you won't be able to get really high CO2 levels, but what you have proposed would work very well if you feel the need! (might be cheaper to fit a small air pump on a timer though! ;) )

As to adding pictures; upload the pictures to a hosting site such as Photobucket.com and then click and insert the URL code with the IMG tags below the picutre you want to insert. HTH.


8 Jul 2007
Cheshire, UK
I found that when running my DIY CO2 on my RIO 180 I could do so very safely without a shut off.

My CO2 levels never got that high as to be a danger to the fish. I actually needed to change the mixture weekly just to keep up.
The only time I potentially could have run into trouble was when I fitted a brand new mixture just as the lights went out. Thankfully I caught my self on and un hooked it until the morning.

If you really want to proceed with the Solenoid then you can do it with a solenoid from lunapeteasily.

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