The Final Word: Refugia and Light/Dark Cycles

[thebanker]

Believe it or not, there is a debate raging in the lounge over the merits of normal photoperiod vs. 24 hour refugium lighting.

Here are the assumptions:

1. The refugium is being run for the purpose of growing chaetomorpha for nutrient reduction. Refugium zooplankton are not relevant to this conversation.
2. The photoperiod could either be a normal light/dark cycle, or run 24 hours.
3. When running a normal light/dark cycle, the best time to turn on the light is when the display tank's lights are off. This is for the benefit of the entire system as a whole. We know this to be true.
4. A normal light/dark cycle is obviously the most natural choice.

Now that those assumptions are out of the way:

1. It is my observation that under 24 hour lighting, chaetomorpha will grow in longer coils, with a lighter green color.
2. Can the chaetomorpha grow 24 hours / day?
3. Can the chaetomorpha engage in "dark cycle events" while the light is on?

 

[3D-Reef]

I don't recall where I read it and I doubt if I can find it again,but,it said that cheatomorpha absorbed more nutrients on a 18on/6off schedule than with a 24/7 photo period.Maybe an indication of why it's light green with a 24/7 period.(?)
It also said that it takes as little as 6 minutes for cheato too complete it's dark cycle needs.

 

[disc1]

We discussed this in RD not long ago too. I get that 24hr lights aren't natural, but neither is most anything else about an aquarium vs the ocean. I don't think chaeto grass can tell the difference. Personally, I don't give algae credit for being very smart. I don't know that it needs any darkness to live.

I think 24hr light, the chaeto probably thinks that the world stopped spinning and it hit the jackpot on the light side.

 

[thebanker]

This was a previous post I made on the subject with a poll for the popular concensus.

http://www.reefcentral.com/forums/showthread.php?t=1927771

 

[ajn81]

Refugium zooplankton are not relevant to this conversation.

I know you said it's not relevant, but I'm curious, would the idea of wanting to preserve zoo-plankton in the refugium make one more likely to go with the reverse lighting system?

 

[thebanker]

If that's the primary motivation for having a refugium, then sure. But for the purpose of this conversation, the goal is maximum chaetomorpha growth for nutrient reduction.

 

[Randy Holmes-Farley]

We are supposed to answer questions for lounge lizards?

Do we come to the lounge to talk chemistry?


FWIW, I've used both ways over the past 15+ years, for both Caulerpa racemosa and chaetomorpha. I've not found there to be a big difference, and I currently use about 18 h on since it obviously ues less energy and costs a bit less than 24 h on.

I discuss some reasons to use less than 24 h on here, but it proves nothing about chaeto in reef tanks:

Photosynthesis and the Reef Aquarium Part I: Carbon Sources
http://reefkeeping.com/issues/2006-10/rhf/index.php

from it:

Photosynthesis of Algae in Continuous Light vs. Light/Dark Cycles
Interestingly, three marine microalgae, Skeletonema costatum, Phaeocystis globosa and Emiliania huxleyi,24 were studied for their rates of photosynthesis and carbon uptake mechanisms in continuous light vs. those same species in light/dark cycles (12 h on/12 h off and 16 h on/8 h off). The rates of photosynthesis were nearly twice as high with light/dark cycles as with continuous lighting. In two of the species (S. costatum and E. huxleyi), but not the third, the contribution of bicarbonate to the total carbon uptake increased dramatically in light/dark cycles compared to continuous light.

How this result might relate to growth and nutrient uptake in lit refugia where macroalgae are often grown to export nutrients is not known. However, it is a sign that perhaps continuous light is not optimal, in addition to being more expensive.

 

[thebanker]

Thank you Randy. We certainly appreciate your scientific input!!