Darren Baucum's Refugium Page

Refugium Page
by Darren Baucum

WHAT IS A REEF REFUGIUM?:

I stole the following definition from Chris Paris because he sums it up so well: "A refugium is a body of water that's physically separated from the main aquarium, but shares a common water supply with it. (One) purpose of a refugium is to provide a refuge for animals and(/or) algae that suffer from excess predation in the main display tank. The (net) effect is to increase the diversity of the whole system beyond that possible with a single tank of similar size." Synergism--the whole is greater than the sum of the parts!!!

WHY HAVE A REEF REFUGIUM?:

There are no hard and fast rules for setting up a refugium. The type of refugium you set up should depend on the reasons why you want the refugium. The primary reason why I added a refugium to my reef aquarium was an attempt to lower nitrate levels which were about 30 parts per million (ppm). I saw a couple of news group postings stating that after adding a planted refugium to a reef aquarium, nitrate levels of the aquarium dropped to undetectable levels, so I gave it a try and it worked for me as well. The theory is that as the algae grows, it takes up various nutrients, such as nitrate, phosphate and ammonium, out of the water. The algae can then be occassionally pruned and thrown away. Macro algae can be given to a friend, sold to the LFS or fed to your fish. There are numerous types of refugiums such as deep sand bed, surge, slow flow, fast flow, planted, live rock, sump, fauna, plankton, lit, unlit, and many combinations of the above.

I have a 37 gallon reef tank with ~70 lbs of aquacultured live rock, 3-4" live sand bed, BakPak skimmer, and no sump. Before I added a refugium, I had about 3 inches of live sand (actually a live crushed coral mixture from Tampa Bay Saltwater, Indo Pacific Sea Farms, and Aquatic Specialists), and my nitrates hovered between 20-30 ppm for 8 months. I added the refugium which contains 3-4" oolitic live sand and flora and fauna kits from Inland Aquatics. I also added an inch of oolitic sand to the main tank. Within a month, my nitrate level dropped to near zero when measured with a Salifert kit and has stayed there for over 7 months now. Also, my skimmer has slowly been outputting less and less skimate since I added the refugium.

Disclaimer: My nitrate drop could conceivably be due solely to the additional 1 inch of oolitic live sand I added to the main tank, but I doubt it. This sand has mostly sifted to the bottom of the tank now. The nitrate drop is almost certainly due to the massive increase in plant life.

This pictures shows my refugium which sits above the main tank. It contains various macro algae purchased from Inland Aquatics as a refugium flora kit. Per their web page, their flora kit may contain the following algae; Heymenia sp., C. brachypus, Grassilaria sp. "Kelp", red Ochtodes sp., and Ulva/Ulvacious. I received 4 different types but I'm not sure which four. I also have hair algae and various fauna such as amphipods, copepods, peppermint snails, bristle worms, chitons, gammarus sp. (mysid shrimp), ophioderma appressum (miniature brittle stars), stomatella varia ("cap snails"), and terebellid sp. ("spaghetti worms").

This picture shows the external refugium plumbing. The valve was added to the return in an attempt to minimize overflow noise. This was ineffective, as the valve stays wide open at all times. The water level in the refugium occasionally begins to rise, and the valve has to be closed and reopened to regain full flow. When using a bulkhead as a surface skimmer, there is no room to build up head in the return pipe without overflowing the tank. To use this valve method you must have an overflow box that will allow head pressure to form. I plan to remove the valve soon before it floods my carpet. A second overflow is a good idea since algae can easily cover the outlet.

The outlet on the left is the return line from the refugium. The Maxi Jet 1000 in the back right corner provides water flow to the refugium. The outlet at the surface of the water carries diverted water from the powerhead that feeds the refugium. Locating the outlet at the water surface has the added benefit of disturbing the water surface, which increases gas exchange, keeps the water surface clean, and causes glimmer lines from the metal halides. I felt that I needed this surface agitation because this system has no surface skimmer and a film would occasionally build up on the water surface.

This picture shows the in-hood plumbing featuring a tee and valve on the powerhead output. The tee and valve are used to control the flow rate through the refugium very accurately, by diverting a portion of water flow back into the main tank.

REFUGIUM SETUP AND MAINTENANCE:

I first added about 3-4 inches of live oolitic sand, then added flora and fauna starter kits from Inland Aquatics and one piece of live rock. I clean the sides and front of the tank once in a while to allow easy viewing. I put in two small astrea snails to help clean the glass, but they do not keep up very well. I clean the overflow outlet cover once every week or two as it tends to collect pieces of algae. I did not put in any hermits, shrimp, or other predators that might decimate the fauna in the refugium. The lights are on a semi-reverse light cycle from the main tank and stay on 14 hours per day. The light source is a 60W Sho Gro incandescent bulb. The flow rate through the refugium is about 20-30 gal/hr. I adjusted the flow to just enough to keep the temperature down while the light is on. I have seen where some notable reef authorities recommend having a refugium turn over rate similiar to that of the main tank. My main tank turn over rate is ~15-20 turn overs per hour and the refugium is at ~5-6 turn overs per hour. The refugium is fed a variety of food (at least as much food as the main tank)--including flakes, Sweetwater Zooplankton, ESV Spraydried Phytoplankton, and DT's Marine Phytoplankton. IMHO, a refugium does not replace the Berlin system, a Natural Nitrate Reducing (NNR) system, or any other system; but it does compliment most methods nicely.

REFUGIUM PLACEMENT:

Placing the refugium above the main tank allows for a free flow of the critters back into the main tank without going through a pump and also allows easy viewing. Locating the refugium in your sump or beneath your tank is fine as well. Some critters will get shredded in the pump on thier way to the refugium but something will likely still eat them. Note that "Dynamic Aquaria", 1998, by Walter H. Adey and Karen Loveland, page 27, states "The unfortunate diffculty with most impellor pumps is that their internal turbulence, pressure, and shear forces kill many plankters and the swiiming or floating reproductive states of plants and animals. We have been able to demonstrate a greater than 90% mortality of large zooplankters, such as Artemia salina, on passing through such a pump." The primary problem I foresee with locating a refugium in your sump is that the water flow rate through a typical sump may be too high and could carry away some critters before they can reproduce and become established. An average sump is 20-30 gallons with about 15-20 gallons of actual water. An average return pump puts out 500 to 800 gallons per hour or more. So the turnover rate for a typical sump is ~30-40 turnovers per hour or more. I think that water flow rate is too fast. I think that anything between 3 and 15 turnovers per hour is probably fine.

ADVANTAGES TO INCLUDING A REFUGIUM:

1. You can grow macro and micro algae in your refugium. This will take up unwanted nutrients, such as nitrate, from the water as the algae grows. Occasional harvesting of the algae is a good form of nutrient export which can then be fed to herbivorous fish. The fast growing micro algae types like hair algae are probably best at taking up nutrients but I much prefer the look of macro algae.

2. Critters can reproduce in the refugium without predators eating them up (hint--don't put predators in the refugium). The critters and their larvae will occasionally flow back into the main tank, providing a good food source and helping to keep the main tank seeded with fauna.

3. You can light the refugium on an opposite lighting schedule as your main tank. This will help to minimize pH swings in the tank. When the lights are on and photosynthesis is occuring, carbon dioxide is taken up, oxygen is given off and pH tends to rise. When the lights are off, respiration from all those photosynthetic organisms gives off carbon dioxide which causes pH to decrease. A reverse light cycle will at least partially offset pH swings.

4. You'll likely get just as much fun and enjoyment from watching the refugium change and develop as you get from watching the main tank. You should at least see a different group of critters in your refugium with no predators present.

ADDITIONAL REFUGIUM-RELATED LINKS:

John Rice's Fauna/Flora Sump
From Albert Thiel's web site 1
From Albert Thiel's web site 2
EPARC News Letter, March 1998
EPARC News Letter, April 1998
Chris Paris' Refugium
Home page with a picture of a refugium
One of Larry Maras' Refugiums
Ken Uy's Refugium
Dougs's Refugium 101 Page
Dana's Refugium
Rocky's Refugium
Scott's Refugium
Kevin's Refugium
Schematics for an Under the Tank Refugium
Deep Sand Bed Refugium
Reef Maniac's Refugium
Skipper's Refugium
Steve Gotz's Refugium
THE ALGAE TANK Page, by Joaco Meier, a very informative page concerning the benefits of harvesting algae with documented test results

Please e-mail me with any comments, corrections, additions, or complaints. I would especially appreciate any good refugium-related links or additional advantages to having a refugium that you know of.