This article is a quick attempt to give you an easy-to-build wet/dry filter. In my case this was designed to filter a 145-gallon pre-drilled aquarium with a built-in overflow chamber. If your tank does not have an overflow chamber, see DIY - Overflow, Skimmer & Sump. This article does not go into great depth concerning some aspects of this project. For more detailed information on constructing sumps, see Building Sumps.

I custom made my stand, so I made it with this filter in mind. The stand is 24” wide and 32” tall (on the inside) This filter is 15” wide and 13.5” tall so you cannot use a standard 12” wide aquarium for your sump. I’ll give you the specifics on my construction; however, you may find alternative products that will work just as well or better.

Parts Needed:

Available at a general discount store

• (1) Sterilite model 3720 2-drawer cart


• (1) 50 Gallon plastic container for sump


• (1) acrylic 11x14 box-style picture frame

Available at a home improvement store

• (1) 4’ long section of “L” shaped plastic wall corner protector 1”x1” (not the self-adhesive kind)


• (8) nylon machine screws, washers and nuts


• (1) sheet of plastic eggcrate


• PVC pipe and 3-way fittings (I used ½” and ¾” – size isn’t that important)


• Bio Media


• Floss Filter

Tools Needed:

• Power Drill with various size bits


• Holesaw bits


• Screwdriver


• Tape Measure


• Saw or pvc cutter

Instructions:

First you need to separate the 2 sections of the drawer cart. (we only need half) The 2 sections are connected by a plastic tab/socket system. You can carefully use a flathead screwdriver to release the tabs and separate the cart. You will want to use the top half because it has a top or cover.

You need to make slide rails for your drip tray to rest on. Cut the corner protector into 4 12” sections. Evenly space and drill 4 holes into the side of the corner protector. Make 4 matching holes into the side of the drawer. I did this about 2.5” below the top of the drawer – you may need to adjust the height. Make sure that your drawer will open and close keeping in mind your plumbing poking through the top. I doubled up and used 2 corner protectors per rail to make sure it could support the weight of the drawer when filled with water. Use the machine screws/nuts/washers to secure the rail into the side of the drawer. Do the same on both sides of the drawer. You may want to wait to actually attach the rails until after you have assembled the bioball cage. Otherwise it can be tricky to fit the eggcrate inside.

Take the plastic picture frame and using a ruler and a washable marker (those overhead markers work great) mark off lines every ¾” along all 4 sides, then use a straight edge and draw lines to make a grid. The intersection will mark where you drill your holes. Be sure to leave a 3” square section in the center undrilled, so the water from your overflow gets evenly distributed. I made 1/8” holes, but you may need to go larger or smaller depending on your desired flow rate.

Drill a dozen or so ½” holes in the bottom of the file drawer. This will allow the water to flow into your sump.

You will need to drill a hole at the top of the drawer for your plumbing from your overflow. Size will depend on the plumbing and method you use to attach to this filter. Make sure to line this up so the water hits your drip tray in the undrilled area.

Since the drawer is slightly larger than the 11x14 drip tray I used eggcrate to square up the bio chamber and ensure that all the bio media was directly underneath the flow from the drip tray. This also creates space for a second prefilter media. Cut the eggcrate to fit snugly along the front back top and bottom of the drawer. I cut the top piece so that it had the “prongs” sticking out and it allowed me to feed it into the front and back piece to hold it elevated. This will also be a place to hold a sponge or floss prefilter. The bottom eggcrate piece just makes sure the bioballs don’t block your drain holes in the bottom.

Choose your media for your prefilters. Sponge, micron, floss etc and outfit your drip tray. You can place something above the eggcrate and below the drip tray if you desire a secondary prefilter.

Using ½” and ¾” PVC I constructed a stand to hold the bio drawer higher in the sump to allow a larger volume of water in my sump without submerging the bioballs. You will have to adjust the height to compensate for the size of the sump, and the height available in inside of your stand Be sure to take into account the additional room required for plumbing, especially in a predrilled tank.

My dimensions are as following:
Inside tank stand 32”
Bio drawer 13.5”
overhead required by plumbing 9.25”
Biofilter stand 9.25”

Here’s the filter sitting in the 50 gallon sump. Just add your plumbing, pump, and heaters and you are ready to go.

The shot on the right is the revamped model using the new stand and eggcrate cage with extra spots for media

The drawer will hold around 5 gallons of bio-media using the dimensions given here. I used 5 gallons of Bio-balls from Big Al's, as displayed in the pictures above.

One last (un-related) note. I wanted a Durso Standpipe, but didn’t have room for 2 - 90 degree turns in my overflow chamber. To solve this problem, I cut out a section of the PVC pipe sitting in my overflow chamber. I then glued a PVC cap to this pipe. The result was a noise-free and space-efficient standpipe.

I hope you find these plans helpful. This filter has worked for me and at a fraction of the price you too can have a commercial-grade Wet/Dry filter for your aquarium. □