How To Build A Cheap Hang On Back Refugium

Updated: Sep 27, 2020

I’ve written before about the benefits of a refugium and macro algae. But how can you get those benefits in a small tank with no sump?

That’s the question I sought to figure out when setting up my temporary frag tank. And I did.


Ok, so why do I have a temporary 10 frag tank? Quite simple actually . . . Petco was having the $1 per gallon sale (also going on now by the way!) and I got my kids their freshwater tank. My wife told me to just buy another 10 gallon hospital tank and not bother cleaning the dirty one sitting in my garage. I had no plans to throw a perfectly working tank out but when your wife gives you permission to buy a tank, you do! So I got what was supposed to be a hospital and/or quarantine tank. I filled it with a few new corals to test its quarantine abilities but soon thereafter joined the World Wide Corals Coral Club where I get sent new corals every month! Sweet! But now I need a permanent tank to house those incoming corals…

Well, I thought, I’ll just incorporate this into my current build. I’m building a 40 gallon reef (which will be detailed at my aquarium build page) that I was planning on plumbing into a larger sump with my BioCube. Now, I’ll just plumb the frag tank into that too. In total, I’ll have a 120 gallon system and multiple tanks allowing me to house different species that normally wouldn’t get along. #Winning!

I know what you’re thinking, “Ok Andy, but don’t you still need a hospital tank and didn’t your wife already tell you to go crazy at the $1 dollar per gallon sale?” Yes, reader, you are right. I give you . . . my garage:

And I know you’re next thought too “Andy, if you are plugging the frag tank into the system, why do you need a temporary refugium and filter?” Good question. The simple answer is that life gets in the way and the build is taking longer than I thought. In the mean time, I needed something to filter my frag tank to make sure my newly acquired corals were happy.

How I Built A Hang-On-Back Refugium for $60

Given that I needed a filter for this tank, I knew I was looking at spending at least $20 for a simple hang on back filter. For $34, I picked up the Aqua Clear Filter. This filter comes with a chamber for mechanical and chemical filtration (which we will remove). I then picked up a piece of mesh canvas from my local crafts store for under a $1; if you don’t have a local crafts store Amazon carries them as well. The next thing you need is Aquarium safe silicone. I had some laying around from when I built my sump. If you are going to be building a sump or conducting a larger project, I suggest you pick up something like Aqueon’s product that can be loaded into a silicone gun. If you are just doing this project, a smaller tube not specifically made for aquariums (but aquarium safe) will suffice. DAP’s product is a good one.

For filter media, I used the bioballs that came with my BioCube. One of the first BioCube Hacks I did was removing those bioballs and putting a media rack in the second chamber to store Purigen and ChemiPure. Knowing I was going to be making the hang-on-back refugium and filter, I placed the bioballs into a ziplock bag, punctured some halls and placed the perforated bag into my sump to allow the balls to grow some beneficial bacteria.

Once I removed the medial shelf from the the Aqua Clear Filter, I cut a piece of the mesh canvas to create a little separation from the mechanical filtration, i.e. the small piece of filter floss I would cut to size and the ChemiPure Nano media that combines perigean and carbon. I also siliconed a piece of mesh canvas blocking the return portion of the filter so my macro algae wouldn’t spill out to the tank. I then took a small, golf ball size piece of Chaeto from my main sump and placed it with the bioballs into the bigger chamber of the Aqua Clear filter.

The only thing missing was a light to grow the Chaeto. I wanted to be efficient; this is only temporary after all. So I picked up this $24 hydroponic grow light. It’s size is perfect for the Aqua Clear filter. To secure it to the filter, I used some good old-fashioned Duct Tape. My father and I used to love watching the Red Green Show about a Canadian Redneck. Red used to say “if you can’t fix it with duct tape, you aren’t using enough duct tape!” In this instance, I went with a black duct tape in order to cancel out the light and concentrate on in the Chaeto.

The end results were:

The filter is growing Cheto, there is currently no algae (other than some film on my glass) in the frag tank and things are going well. While this was just used as a temporary filter, I will out put the bioballs and sponge back in my sump when I’m done with the tank and have this handy-dandy filter ready to go next time I need a quarantine or hospital tank.

Questions? Leave them in the comments or reach out to me directly! Don’t forget to sign up for our mailing list below so you don’t miss out on any tips, tracks or hacks.

Happy reefing!

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