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refugium design


Sep 10, 2007
I am planning an O. habitat for my high school Marine Biology classroom. I have a 75 gallon acrylic tank. A generous Tonmo member has offered the use of a chiller. I am near Monterey CA. I keep my tide pool tank at 56 F.
Now I am planning a refugium to connect the chiller to the tank water, provide a place outside the tank for treating the water, and give me a place to keep crabs, shrimp, mussels alive before they go in the tank with O.
The refuge I am thinking about would have three sections with water spilling from one to the other. The first and tallest one would have my protein skimmer. The next one would have an undergravel filter covered by coral gravel with a powerhead to pull as much water as possible through the gravel. The shallowest part would be the refuge with sand and a rock in the middle that is above the water for shore crabs (the hate to stay underwater for long).
I plan to have easy access to siphon clean the gravel and empty the protein skimmer without having to disturb or provide an escape hatch for the O.
What do you think?
I think you are way ahead of the game by taking into consideration the space for easy access to the sump - our next tank WILL have easier access than our current 140!

The undergravel in the sump sounds interesting but why not just use LR in the middle section (or a deep sand bed for nitrates) and not have the gunk collect and clog? I would never (never say never ;>), use an undergravel again, even our modified ones don't work well after a year or so.
You truly are ahead of the game...sounds like you've really thought this out.
I really like the design as a whole, but agree with dwhatley - undergravel filters can be a pain, you can use just the crushed coral and some LR to achieve the same filtration.
Although I have nowhere near the complexity you are planning in your refugium, I use a similar process for filtration. Instead of using a filter system, I use just sand/crushed coral *as* the filter [run a tube with a VERY low GPH powerhead straight through the bottom of the sand bed]. The important thing is to have a very slow flow through this part of the refugium, but it has done wonders to help regulate levels. The beauty of that kind of setup is that you can introduce some sand sifters/cleaners to the refugium to help keep your "filter" clean such as sifting stars or tiger nassarius....or even a sifting goby if you can provide it with a little light.
Another thing you might want to try adding, and this has some mixed reviews, is Chaetomorpha. It is known to reduce nitrates and phosphates - it isn't the "miracle" solution some people think it to be, but it definitely does help.
Good luck, and show pictures when you set that up, I'm really interested in seeing what you come up with! :biggrin2:
Thanks for your comments. I have had good luck with undergravel filters; they can be used to take out large particles that cloud the water in addition to being good biological filters. I do not mind siphoning them out once or twice a week.
Now if I could figure out a way to grow cold water marine algae without huge blooms of clogging filamentous algae I would be good to go. I guess I may have to go with a plantless tank and refugium.
Next step is to locate that refugium.
thanks again
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