Optimum Lighting WPG


Expert/Global Moderator
Staff member
11 Jul 2007
Chicago, USA
No, circulation does not dissipate the CO2. Splashing the surface would do that but increased movement around the tank won't. Moving more water around the tank brings low CO2 areas into contact with the dropchecker as well as mixing low CO2 water with higher CO2 water. The result is that you see an average CO2 content of the mixed water. If the dropchecker goes dark then you know that the average of the mixed water is low so you should add more CO2. It's entirely possible that when you had poor circulation the dropchecker was exposed only the segment of the water that held a higher CO2 level, while the rest of the water had lower saturation. I call this "Stage I Illusion" due to dropchecker hypnosis. You must observe the plants. They are the real dropchecker. When you see CO2 related algae you must immediately stop believing the dropchecker because it's only one rudimentary indicator. This is why when someone says; "I have BBA/Hair/Staghorn but my CO2 is fine because my dropchecker is green" then I conclude immediately that their CO2 is NOT fine. Dropcheckers lie. BBA never lies...

CO2 concentration is never equal across the tank. It will be high in some areas, medium in others and will be low in yet others. In the same way the water nearest the heater is warmer than the water in areas furthest from the heater. Imagine shutting off the filter so that there is no water movement. The difference between the warmest areas and the coolest areas would be stark. More flow helps to create a more even distribution by mixing warmer with cooler to even things out. CO2 concentration and nutrient concentration are affected in exactly the same way.

You need to turn on the CO2 earlier and you need to inject a higher rate so that by the time the lights go on you will have achieved better mixing and better average concentration levels. Ideally, the dropchecker should be lime green at lights on and your plants should begin to pearl within an hour or two of lights on. This is how to keep BBA and other CO2 related algae suppressed. Adding liquid carbon reduces the pressure to add so much gas so if you have sensitive fish Excel/Easycarbo can help to supplement the Carbon consumption and to lower toxicity issues.

Hope this helps. ;)


Dolly Sprint 16v

Thread starter
26 Oct 2008
That what I was trying to say - I new what I wanted to say but it puting in the right context so people understand what you are trying to say.



Thx mate Co2 levels going up this weekend.

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