WPG threshold

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oxymoron

Aquarium Advice Regular
Joined
Apr 22, 2005
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Fort Wayne IN
At what WPG threshold do you need to start considering a CO2 injection system? Just curious, I'm only at 1.5 WPG now.
 
Never mind, I did some looking and found that the consensus is CO2 is not necessary if you are under 2 WPG. Anyone disagree with this?
 
I would'nt exactly disagree, But you have to take into account the type of lighting
and the quality of the reflectors used for the lights.
2WPG of T5-HO with great reflectors is more light than 2WPG of regular NO lights with poor or no reflectors.
I think that the WPG rule is geard towards regular NO lights.
 
Alex makes good points. The wpg 'rule' is just a loose guideline, and is indeed based on NO fluorescents. Thus when using PC's or VHO's, you can cheat a little bit. Good reflectors of course prevent loss of light, which helps even more.
(however no reflector actually 'doubles' your light to twice the rated wattage...its a legit claim though because without reflectors you're losing half the light from the top of the bulb, so any efficient reflector design will bring you back up to full wattage aimed into the tank)

as for my opinion on the threshold, I say 2wpg is when you should start injecting CO2...but at 1.5wpg of VHO or PC lighting, CO2 will have a positive effect on plant growth. Below 1.5wpg I don't think it's worth the hassle, though I've seen a few hobbyists who experimented with it, and did seem to have bushier growth.
 
Another advantage of CO2 at low light levels, according to Tom Barr and others who have studied its effects, is excellent control of algae. Additionally, water changes are not nearly as necessary and you can go much longer periods without much tank maintenance at all.
 
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