Algae growing light cycle

[TheGooseWhisperer]

Just wondering what the deal is with turning the lights on for macro on a reverse cycle. Nature doesnt work this way so why is it that we do it as reefers? Does anyone grow their macro on the same light cycle as the DT? if so what do you notice?

[Mitchell]

Its to keep the ph more stable.

 

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[Drew]

Its to keep the ph more stable.

+1

 

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[finch6013]

I'll add that also it will help with heat issues on heat sensitive tanks. Also depending on how the utility charges you, electricity is generally cheaper at night.

[Eugenereef]

The reason which pH is stable by keeping the refuge lights in reverse cycle is following:

 

During the day time, the corals are generating energy (sugar synthesis) by photosynthesis and hence they use CO2 and give out O2 (just like plants), however, in night, the process changes to respiration where they use O2 and give out CO2 (catabolism, using sugar). As the amount of CO2 goes up, the pH of the tank water and vice versa.

The macro also undergoes similar cycle of photosynthesis and respiration. If you keep the refuge light on with tank lights, both the macro and corals under go photosynthesis at the same time, thus using a lot of CO2 and hence the rise in pH. At night however, they both will give out a lot of CO2 due to respiration and the tank pH drops.

To address these fluctuations, if you put refugium in reverse cycle, then one half of the tank is always undergoing photosynthesis and the other half is under going respiration, and then at night the roles reverse. This keeps the amounts of CO2 in check and hence a stable tank pH.

Even if you have a good refugium, you will see the pH fluctuations, like the one shown in this pH data chart!

 

 

This is a daily report:

 

and this is a weekly report:

 

You can clearly see how the pH is going up and down during the day and night.

 

Hope this clears the confusion!

[TheGooseWhisperer]

Thanks Eugenereef! I was aware of the principle, but the graphs really drive it home. I was unaware that there was this much fluctuation even with a refugium on a reverse cycle. With both on the same light cycle the swings would be significantly bigger. I guess you could tweek the amout of macro to try to minimize the extent of swing, but with the day/night transitions there will have to be some fluxuation.

 

My issue is that I dont have the back of the tank painted and there is substantial light coming out of the back of the stand. I'm going to get some dark heavy fabric and tack it on the back of the tank, but then I'm worried about the humidity inside the stand. Guess we'll see how it goes.