DIY Acrylic Refugium

Refugiums are a terrific new addition to saltwater aquarium systems. Refugiums can be used to hold a myriad of things, including nitrate reducing Mangroves and Algae as well as 'Pod Farms for cultivating Amphipods and Copepods. The Hang on and Hang In Tank type refugiums are the most popular due to their ease of installation and simple or no plumbing requirements. Here is a photo of a small (4" X 6" X 8" high) acrylic Hang On Tank refugium with Mangrove seedlings, being used to reduce nitrates, phosphates and other toxins in a 55g saltwater tank. The plumbing is simple: a siphon tube and a small plastic hose from the top of a powerhead. This refugium can be hung anywhere on the outside of a tank or sump. You can also drill some holes in it and hang it on the inside of a tank or sump, which requires no plumbing. Refugiums can be constructed of glass, acrylic or just about anything else that will hold water, however here we are going to show you how to build a Hang In/On Tank Refugium using 3/16" Cell Cast Acrylic.

Exploded View of the Acrylic Refugium

Acrylic Refugium Exploded View
Here is an exploded view of a typical hang in or hang on tank refugium. You can make your refugium any size you wish. We suggest that you click on the graphic to see the enlarged version and then print the diagram. You can use this to make notes for the dimensions of your refugium. You will want to adjust the size of the Bracket to accommodate the thickness of your tank or sump wall material.

DIY Acrylic Refugium Parts List

If you can not find them locally, a 24" by  24" sheet of 3/16" Cell Cast Acrylic can be purchased from Acrylics USA for about $15.00, plus shipping and handling. A 4 oz. can of Weld-On #4 be purchased from rplastics for about $6.00 plus shipping and handling. The sheet of acrylic will have either a paper or plastic sheet covering when you receive it. Do not remove this paper or plastic sheet while assembling. If you don't want to cut the acrylic yourself, the acrylic supplier will usually do it for you for a small fee. You can find syringes and hypodermic needles at your local pharmacy, although you may be asked a few questions about your intended use. The masking tape and sandpaper can be found at your local hardware store.

DIY Acrylic Refugium Tools

The blades for either the table saw or jigsaw should have as many teeth per inch as possible for cutting acrylics. If you are using a jigsaw, use a blade with 16 to 18 teeth per inch. If you are using a table saw, the "fine cut" blades will work best for cutting acrylics. This will produce a much cleaner cut which will require less finishing prior to bonding. If you plan to make your refugium a hang in tank type, drill holes in the side, bottom and/or front pieces of the refugium before assembling. 1/2" holes will work well for most applications. Use the water spray bottle to keep the drill bit cool while you are drilling. You will find that a slower drill speed works best for acrylic.

DIY Acrylic Refugium - Edge Finishing

Use a flat, smooth work surface, such as a piece of glass or a tabletop for this fast, simple method for removing cutting marks on the acrylic edges. Place a sheet of 320 grit Wet/Dry sandpaper on the work surface. Pour a small amount (1/8 cup) of water on the sandpaper. Place a piece of 2 by 4 on the sandpaper. Hold the acrylic piece against the side of the 2 by 4 (this will keep the acrylic edge flat and square) and move it back and forth until the desired effect is achieved. Apply even, downward pressure on the entire piece while sanding. See the difference between finished and unfinished edges on the following page.

Finished and Unfinished Edges

Here are two close up photos of the edge of a piece of acrylic, before and after it was sanded.

DIY Acrylic Refugium Pinned Pieces

When you put the pieces together, there should be no visible gaps along the sealing edges. The reason for having flat, smooth surfaces is that when you bond the pieces together, you want to avoid having bubbles in the joint. When you apply the Weld-On #4, it will be sucked into the joint via capillary action. The Weld-On chemically "melts" the acrylic surfaces and then dries, welding the two pieces together. To assure complete distribution of the Weld-On between the two pieces of acrylic, we will be using ball head pins to create a uniform gap and masking tape to hold the pieces in place. You will want to practice with scrap pieces of acrylic until you can bond acrylic with no bubbles and have the pieces exactly where you want them, before moving on to your refugium. Before assembling the pieces, fold the protective paper/plastic back about 1/2" from the bonding area and cut the paper/plastic off with a utility knife or razor blade. Insert 2 pins in the joint and tape the pieces together. Bond only joints which are flat. Do NOT attempt to bond vertical joints. Here is an example of what your pieces should look like before applying the Weld-On. Note that the pieces are even on the ends and edges.

DIY Acrylic Refugium - Weld-On Injection

Now open the can of Weld-On #4 and withdraw about 2 ml of the liquid with the syringe and needle. Remove any air bubbles from the syringe. Starting at one end, insert the needle into the gap between the 2 pieces of acrylic and start pushing the Weld-On out of the syringe as you move the needle down the gap. You will be able to see the liquid fill the gap as you go along. Do not remove the pins when you come to them, instead "jump over" the pins as you go along. You will see the Weld-On fill in around the pins. When you get to the end of the pieces, wait about 30 seconds, then remove the pins. Since the tape is holding it, the vertical piece should remain in place. You will have a few seconds where can gently slide the vertical piece a bit to align it, but do not pick up the vertical piece as this will create bubbles in the joint. Hold the vertical piece in place for about another minute. Do not move the pieces again for at least another 4 hours. Once you have perfected your bonding procedure, it's time to go on to the real thing. What we are going to do first is bond the 2 side pieces to the back piece of the refugium. It will look like this just before you start injecting the Weld-On #4 into the joints.

DIY Acrylic Refugium Assembling the Pieces

In this photo, the back piece of the refugium is laying flat on the table. The side pieces are the ones on top of the pins and the bottom piece of the refugium is at the top of the photo, taped to the side and back pieces. Fold back and remove about 1/2" of the paper/plastic on the bonding areas of the back and side pieces. Leave paper/plastic on the bottom of the back piece and all of the bottom pieces intact. Insert the balls pins between the side pieces and the back of the refugium and tape the pieces in place. The bottom piece of the refugium is taped in place (without bonding) to hold the side pieces of the refugium in place during the bonding procedure. Before you start bonding, your refugium should look like the one in this photo. Next, with the Weld-On #4, bond the 2 side pieces to the back piece and remove the pins. DO NOT bond the bottom piece to the back piece or the side pieces. The protective paper/plastic should still be in place on the bottom piece. Do not move the pieces for 4 hours after bonding is complete. Next, we are going to bond the front piece of the refugium in place. Place the front refugium piece on top of the side pieces. Tape the front piece to the bottom piece. Insert the ball pins between the side and front pieces and tape in place. Flip the refugium over so that the front piece is on the bottom. Using the Weld-On, bond the front piece to the side pieces. If you do not have enough room to apply the Weld-On from the inside of the refugium, pull the tape away from the side pieces, one at a time and apply the Weld-On from the outside of the refugium. As you complete each side, remove the ball pins and replace the tape. When both sides are complete, leave the refugium in place for 4 hours.

DIY Acrylic Refugium - Finished Product

Repeat the bonding process on the 2 bracket pieces. After 4 hours, install the bracket on the top of the refugium, using the same ball pin and tape method. When your refugium is complete, you will want to wait at least 24 hours before water testing. Your finished refugium will look like this:
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