Larry Lunsford

Bead filters have been in use on Koi ponds for several years and have proven to work very well. Bead filters are great for both biological and mechanical filtering. They are compact and simple to operate. Their greatest disadvantage is their cost.

Here's how to construct your own low cost do-it-yourself bead filter. Besides cost, the main difference between this filter and the commercially available filters is the cleaning procedure. The commercial bubble bead filters rely on a custom chamber design and air to churn the beads and loosen debris. This DIY filter uses reverse flow to clean the beads. Many owners of bubble bead filters also use reverse flow to provide better cleaning of their filters. This DIY filter is also much shorter and therefore easier to conceal than bubble bead filters.

The DIY bead filter consists of: tank, beads, flow pipes, and valves. The tank is a 30 gal. or 55 gal. plastic storage drum. You can buy a new drum or you can pick up one free from sources such as food processing plants or your neighborhood car wash (they get soap in barrels). If you're getting a used drum, be sure to get the bung plug for it and be sure to clean everything thoroughly. All the drums I've seen have two plugs: one is 2" pipe thread, and the other is 2" bung thread (a very coarse thread).

You can buy plastic beads for your filter from plastic suppliers or Aquatic Eco-Systems (part AB1 - Filter Beads). Get enough beads to fill your drum half way (2 cubic foot for a 30 gal drum, 3.5 cubic foot for a 55 gal drum). Be sure to get beads that float.

One complaint I've heard about bead filters is that they are slow to culture the desired bacteria. Some have suggested that the slick surface of the beads is the reason for slow bacteria growth. To rough up the bead surface, I put mine in a cement mixer along with some sand and bricks, and let the mixer run for an hour. The sand provides grit to rough up the bead surface and the tumbling bricks provide the force needed to work the sand into the beads. Separate the beads from the sand by dumping the mix into a tub of water - the beads will float and the sand will settle to the bottom. I haven't done any testing to determine whether roughing up the beads really helps. I have examined new and processed beads under a microscope, and the ones that went through the mixer definitely have a roughed up surface.

(Alternate Bead Texturing Process - AKA Bart Simpson Method: Get a clean 1 gal paint can and lid. Fill can with mixture of beads, sand, and rocks. Put in paint shaker. Run like hell??? If you're Bartish enough to try this, let me know how it worked.)

Build Flow Pipes

The only part of this filter that you have to build is the flow pipes. The flow pipes in this DIY filter are better than those in the commercial filters - they have a lot of open surface area to allow easy flow of water, plus they're much longer.

Cut two pieces of 1-1/2" PVC pipe to length. Plug the end of the flow pipes that will be inside the drum. There's several ways to do this. The method I prefer is to use a 1-1/4" threaded PVC plug. To get the plug to fit inside the 1-1/2" pipe, you need to remove some of the material from the inside of the pipe (I used a coarse file). Then you need to tap the end of the pipe for 1-1/4" pipe thread (I used a 1-1/4" metal pipe plug as a tap - see photos). Once the end of the pipe is taped, simply screw in the PVC plug.

Drill 3 rows of 1-1/4" holes in each pipe (use a Forsner bit in a drill press, support the pipe with a V-block). The rows of holes should be at the 12 o'clock, 3 o'clock, and 9 o'clock positions. This leaves an area without holes at the 6 o'clock side. If you don't have a drill press, use a hand drill and just drill more rows of smaller holes (still leaving a strip that's free of holes).

Make adapters for the flow pipes. The adapters screw into the fittings on the drum. For the flow pipe that will mount in the 2" pipe thread hole, use a 2" PVC male adapter and a 1-1/2" x 2" PVC bushing. Glue the 2" adapter / 1-1/2" bushing to the flow pipe (you'll need to grind out the bushing a bit to allow the 1-1/2" pipe to slide through it). For the flow pipe that will mount in the bung thread hole, drill out the drum bung plug and glue it to the flow pipe.

Cover the flow pipes with a layer of fiberglass window screen. I got my window screen at the local hardware store. The label says its pet proof and it really is incredibly strong. Don't use metal screen - it's not nearly as tough and it'll corrode away. Rough up the flow pipe with course sand paper. Cut a piece of screen long enough to go around the pipe one and a quarter times. Put a bead of aquarium safe silicone or epoxy along the hole free area (6 o'clock side) on the flow pipe. Lay the screen on the bead of silicone. Work the silicone into the screen. Put another bead of silicone on top of the attached screen. Wrap the screen around the pipe and work the end into the silicone. Seal the screen around the ends too. Work silicone into the screen in the areas over solid pipe. Be careful not to smear silicone onto areas of screen over the holes. For added security you can attach a clamping strip of PVC (cut from PVC pipe) over the seam - attach the strip with stainless steel or nylon screws (be sure not to make things too big to fit in the drum holes).

If you don't want to spend as much effort making your flow pipes, you can use well screen (also available from AES) which is the same type of pipe used in the commercial bubble bead filters.

Install Your Filter:

Put your beads in the drum. A big funnel helps. Do this in an area where you won't mind a few stray beads lying around (a few always escape and it seems that you can never round them all up again). Put some teflon tape around the threads on the flow pipe adapters. Screw in the flow pipes. You may want to fill your filter with beads near its final installation site - once the drum is filled with beads it's heavy and awkward to move.

Set your drum bead filter in place and plumb it to your pump and pond. The filter should be placed with the drum and flow pipes laying horizontal. The drum should be rotated so that one flow pipe is directly above the other. Your filter should be plumbed so that in normal use water flows in the bottom pipe and out the top pipe. For cleaning, water should be pumped into the top pipe and water coming out the bottom pipe should flow to a waste line.

Since the filter operates under pressure, you can place it just about anywhere. Locate your filter so that it is not subject to too much pressure. If you have a tall waterfall, you may want to place your filter near the top of the waterfall or on a stand so that it won't have to withstand the head pressure required to get the water to the top of the waterfall.

With some minor changes, the drum filter can be used in different ways. If you only want to use the drum filter for biological filtering, you can reverse the flow and keep the beads fluidized. You can also use other types of floating media that are intended for use in a fluidized mode. Don't use a media that can't be well cleaned by reverse flow (such as lava rock or gravel).

There you have it. Happy Koi keeping.

Koi