Refugium lighting

[MasterBlaster]

Can anyone tell me what lighting cycle is best - 24/7, or reversed from the main tank lighting? Why? There will be plants, of course.

[Ninong]

Can anyone tell me what lighting cycle is best - 24/7, or reversed from the main tank lighting? Why? There will be plants, of course.

MasterBlaster,

I was hoping someone else would respond to your inquiry but so far no one has, so I'll give you my thoughts on the subject.

There is no agreement among hobbyists as to which is best when it comes to refugium lighting.

The three possibilities are:

• 24/7
• Reverse daylight
• On simultaneously with main tank

People who favor 24/7 are convinced that it is better in preventing sporulation of the macroalgae. People who favor reverse daylight realize that this mode will be more effective in reducing the variance in their pH readings over a 24 hour period. People who favor simultaneously lighting with the main tank either aren't aware of the concept of reverse daylight lighting or are unable to utilize it for whatever reason.

If I am able to figure out a way to incorporate a refugium into my new setup, I would hope to have it on a reverse daylight program but the refugium's photoperiod would be longer than the main tank's. My preference would be for 16 hours on and 8 hours off for the refugium, although I would also consider 18 hours on and 6 hours off acceptable. My preference for the main tank lighting would be 11-13 hrs on depending on the season.

The reason reverse daylight and 24/7 refugium lighting help level out your pH readings in the main tank is because of the nature of photosynthesis. All plants, including the zooxanthellae in corals and the macroalgae in your refugium, produce oxygen and take in carbon dioxide when exposed to light and give off carbon dioxide and take in oxygen during periods of darkness. It is the respiration of the algae (including zooxanthellae) in your main tank at night that gives off carbon dioxide which lowers your pH. So it would make sense to have macroalgae somewhere else in your system (refugium) that are giving off oxygen while the main tank is giving off carbox dioxide. This would act as a counterbalance to reduce the effects of the carbon dioxide in the main tank.

Please don't ask me about 24/7 lighting for refugia because I am personally surprised that it works at all but many people actually do use it. I guess it just goes to show that algae do not act the same way terrestrial plants do when exposed to around the clock lighting with no rest periods.

I personally do not buy the argument that 24/7 lighting is better in controlling sporulation although I admit that it is possible that is true. Remember, I don't accept the idea of 24/7 lighting to begin with so I would be biased. I prefer to believe that macroalgae go sexual when they reach a critical mass. Lighting obviously affects their growth but I'm not sure you can say that lighting is the main factor in determing when macroalgae will go sexual, I think it is mass. Caulerpa, for instance, is a single cell plant in the sense that it has no cell walls but does have multiple nucleii. It sporulates and dies when it is good and ready just like salmon. So if 24/7 lighting interferes with its normal life cycle, I guess that could be claimed as retarding sporulation.

In any event, if you see your macroalgae turning white, just remove it so that you do not take any unnecessary chances. Sporulation events sometimes cause significant problems.

[scubadude]

I couldnt have said it much better than Ninong However I will add a bit to this just to back up and so you have another opinion.

Of the 3 options that Ninong stated above I would only consider Reverse photoperiod of the tank or 24/7 and the ONLY reason I ever use 24/7 is when I have algae problems in the main tank and im trying to outcompete them with the algae in the fuge.

Rocky

[MasterBlaster]

Thanks for the good explanation, Ninong. I'm curious why a 6-8 hour period of darkness is necessary. Wouldn't 24/7 keep the macroalgae in a constant vegatative state? Why is it necessary to stop photosynthesis?

[organicreefer]

a dark period isnt necessary -even for many terrestrial plants..many of them are grown under a 24 hour light period too-and the lighting period reduced only to promote blooming.

obviously-i favor 24 hour lighting myself .since the main function of my refugium is vegetable filtration-i prefer to keep that macro sucking nutrients 24 hours a day.its been working great for me for two years now-and i dont see any reason to change it.

[Ninong]

Why is it necessary to stop photosynthesis?

Respiration is a part of photosynthesis, too. What you are thinking of is the part of photosynthesis that takes place in the presence of light, the production of sugars, etc., a process that consumes carbon dioxide and gives off oxygen as a by-product. Respiration is the part of the process that takes place in the absence of light and consumes oxygen and gives off carbon dioxide as a by-product. It would be more accurate to say that during the period of darkness there is more carbon dioxide given off than oxygen and during the period of light there is more oxygen given off than carbon dioxide. The same holds true for consumption, too. Perhaps we should say that during respiration a plant consumes more oxygen that it gives off and gives off more carbon dioxide than it consumes. And vice versa during periods of light.

So the photosynthetic cycle goes on whether there is light or the absence of light.

With flowering terrestrial plants, you can manipulate the blooming by changing the period of darkness. If you have plants that normally bloom in November and you want them to bloom in December, just lengthen their exposure to light and if you want them to bloom in October just shorten their period of light -- the important thing here is not the light period, it is the darkness period. So to speed up the blooming, you lengthen the period of darkness; to delay the blooming, you shorten the period of darkness.

I am not aware of any terrestrial blooming plants that are kept under 24/7 lighting indefinitely (for years and years) such as we are talking about doing with macroalgae in refugia.

[organicreefer]

well -one terrestrial plant that is grown in alot of peoples closets ;) is kept under 24 hour lighting by most who grow it..the lighting cut to 12 hours to induce blooming

i also used to date a girl from argentina whos mother grew herbs hydrponically and she said she used a 24 hour light cycle as well.

i think alot of hydroponic gardeners use the 24 hour light cycle to speed up the time between harvests.

[MasterBlaster]

well -one terrestrial plant that is grown in alot of peoples closets ;) is kept under 24 hour lighting by most who grow it..the lighting cut to 12 hours to induce blooming

i also used to date a girl from argentina whos mother grew herbs hydrponically and she said she used a 24 hour light cycle as well.

i think alot of hydroponic gardeners use the 24 hour light cycle to speed up the time between harvests.

What in the world would you grow in a closet? ;; Wouldn"t the clothes get in the way? (I'm so innocent)