in my constant search for better filtration i can across the two sump reverse day light refugium. i understand how to build and the purpose of the refugium but the reverse daylight part has me lost

Hi clown-t ~

All plants, whether zooxanthellae, macroalgae, caulerpa, or oak trees, are net producers of oxygen and net consumers of CO2 during photosynthesis--which takes place in the presence of light--but they are net consumers of oxygen and net producers of CO2 during respiration--which takes place in the absence of light.

Therefore, in a reef tank without a refugium, the CO2 level will rise once the lights are out and the symbiotic algae begin to respire, causing the pH to begin to fall. But, if you were to set up a refugium and stock it with plants--macroalgae, caulerpa, mangroves, whatever--and have the lights come on during the period that the main tank is in the dark, your refugium would be producing oxygen and consuming CO2 to counteract the production of CO2 and consumption of oxygen from the main tank. And conversely, when the refugium is in the dark and the plant life there are net consumers of oxygen and net producers of CO2, the plant life in the tank (zooxanthellae) is now counter balancing the refugium because it is in the photosynthesis phase. The net result is a leveling off of the customary drop in pH at night that would be experienced without the benefit of a refugium on a reverse daylight cycle.

Ninong [img]/ubb/smile.gif[/img]

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Irrational Exuberance!

I have employed the reverse lighting refugia for two years now and have excellent coral growth with a very minute ph swing at night- Works well for growing algae which competes for nutrients in the show tank. The algae is pulled out by the handful on a weekly basis and taken to local distributers for credit [img]/ubb/smile.gif[/img]

Ditto what Ninong states regarding stabilizing Ph. I run my refugium 24/7 though. It's been said that this prevents the Caulerpa from going sexual which I've been told can be bad for your tank.

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"Remember...Wherever you go...There you are."
Buckaroo Banzai, circa 1978