Refugiums

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Refugiums
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Refugium is becoming quite the buzz word in the salt community these days.
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They certainly aren't anything new, but their efficiency and ease of use has reached the mainstream. Not too long ago, 'algae scrubbers' and the like lived on the fringe, accepted only by the Willy Wonkas, those not afraid to try something outside the box, while everyone else, including me, stared at the bubbles in their new venturi protein skimmer.
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Not any more. As live rock, and now live sand, take hold as the foundation of the reef aquarium, people are looking for, and more accepting of, other natural filtration methods. The refugium's time has come.
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What is it?
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So, what is a refugium you ask? It is simply an area located outside of the main tank with tank water flowing through it in which caulerpa, or some kind of macro-algae plant, is grown and harvested. Caulerpa is reknown for its abilities to purify the water by greatly reducing nitrates and phosphates. Lights are put over it for the caulerpa to grow and the refugium also acts as a refuge for filter feeders such as copepods, or 'pods' so to speak. These little squirmies are a big part of a healthy reef and the refugium provides a safe haven for them from the inhabitants of the main tank.
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A refugium can easily and cheaply be set up and maintained and this fact will undoubtedly be the key to its success. Simply dividing an existing sump is possible if you have room. However, many use another sump altogether to act as the refugium. As with all sumps, this can just be small aquarium.
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<img src="http://www.3reef.com/fish/sitepics/aboverefugium.jpg" width="250" height"213">
<div class="caption">Above Sump Refugium</div>
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Placing the refugium higher than the sump allows you to drain water from the refugium back to the sump via gravity. The overflow from the main tank drains directly into the refugium before going down into the sump. The overflow can be teed off to control flow into the refugium, with the reminder being diverted into the sump. Finding the right flow rate is key for maximum filter efficiency.
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Likewise, placing the refugium higher than the actual aquarium works as well, with a powerhead in the aquarium providing the water or, alternatively, pumping water from a sump into the refugium which then drains into the aquarium. There are other options including hang on the back models like CPR. However you set it up, just make sure that you have eliminated all flooding possibilities in the event of a power failure.
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<img src="http://www.3reef.com/fish/sitepics/aquafuge.jpg" width="250" height="213">
<div class="caption">CPR Aquafuge 'Hang On The Back' Refugium</div>
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Looking at people's refugiums on the Internet, I was surprised to see many people using rather large aquariums as refugiums with not much caulerpa. To me this defeats the purpose. What I have had in mind for my own refugium is something similar to Aquaricare's Algae Scrubbers. A shallow refugium will receive maximum light intensity with smaller lights than a deeper one resulting in maximum algae growth and filter efficiency.
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Therefore, I have been eyeing things like paint roller trays or shallow, long plastic containers to place above the sump. I also have been thinking about setting a rectangular piece of egg crate inside. Lightly quick-tieing caulerpa on it, this will act as a removable holder for quick periodic cleaning and removal of excess algae. It will also prevent the caulerpa from bunching at one end of the refugium.
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<img src="http://www.3reef.com/fish/sitepics/algaescrubber.jpg" width="250" height="177">
<div class="caption">Aquaricare Algae Scrubbers</div>
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Another great thing about refugiums is that you don't need expensive lights to grow caulerpa. Caulerpa is like a weed and needs little encouragement to grow. If you have been in this hobby long enough, you probably have some extra fixtures or ballasts laying around and most likely they will work great. Unlike the aquarium which may require in the neighborhood of 3-5 watts of light per gallon, you can probably get away with less in the refugium. Of course, this is especially true with shallow refugiums. You don't have to be too picky with bulbs either since, for once, you are actually trying to encourage algae growth. Wow!
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I should note that some have such good results with refugiums that they no longer use their protein skimmers, I feel this is a mistake. Protein skimmers do a lot more good than bad including add a lot of oxygen to your water. This is often overlooked. I realize caulerpa also adds oxygen to the water, but the merits for keeping a protein skimmer are many. Keep the skimmer.
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With this hobby is seems you can't have a single methodology that doesn't have opposing camps or splinter groups. Refugiums are no exception. Among those that use it there is a divergence on the proper light cycle. Many simply leave the lights on 24/7 and there are good reasons for this. With 24/7, maximum growth rates are achieved and the caulerpa is prevented from going 'sexual.' What this means is that with pronounced dark periods, like many plants, a hormonal change will occur in some common caulerpa strains like grape caulerpa and spores will be released clouding the tank and making algae blooms and caulerpa growing in the main tank possible. Leaving the lights on in the refugium also prevents pH swings that can occur with opposite light cycles between the aquarium lights and the refugium lights.
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<img src="http://www.3reef.com/fish/sitepics/grapecaulerpa.jpg" width="250" height="216">
<div class="caption">Grape Caulerpa</div>
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<img src="http://www.3reef.com/fish/sitepics/razorcaulerpa.jpg" width="250" height="208">
<div class="caption">Razor Caulerpa</div>
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So why would anyone want opposite, or reverse daylight, light cycles? Well, for one, it is more natural. A real reef receives oxygen rich water at night from deep sea tidal currents. Likewise, a reverse daylight setup creates a symbiotic environment where one source is releasing oxygen and consuming co2, while the other is releasing co2 while consuming oxygen. The pH swings can be prevented by having slightly overlapping light cycles. And using certain strains of caulerpa such as teacup and razor will help reduce the chance of spores being released. Other benefits include longer bulb lifes and less electricity consumed. In addition, refugium filtration will be more efficient due to detrifying bacteria and pods that prefer the dark to light.
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Rather than push you one way or the other, especially since I am still learning this, I would rather leave it open ended. Lets just say that going 24/7 is easier and provides a lot of insurance at the cost of a little filter efficiency. Going with a reverse daylight setup is more challenging with more pitfalls, but has the most potential for best results.
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I hope this helps.
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good spread matt

 

Great article Matt. Luna

 

Nice. I'm thinking of replacing my Canister with a fuge.

 

I've always heard go opposite lights with a 'fuge...I never knew that lights on a fuge 24/7 would help...This puts a whole new spin on things...

 

Thats what my LFS told me the other day. Even thou I dont have Caulerpa(to go asexual) it just doesnt seem natural to have the lights 24/7, esp. when that doesnt exist in nature. Luna

 

wise choice

 

yeah exactly, so this article is saying that in order to prevent caulerpa from going sexual, you should have your lights on all the time...that goes against everything i've read!