Bio Filter Media for Ponds and Koi

2/12/76Bio Filter Media by Werner rev 06/08

Overview

Bio Filtration takes place in all the nooks and crannies of your pond, including your plumbing pipes, liner and tubing. The brown slimy deposits that accumulate in your pond plumbing are colonies of beneficial bacteria or Bio Film Colonies, creating what is known as the nitrogen cycle. For years, "lava rock" has been used as a bio filter media with good results. There are however, much more efficient, tested and proven media on the market today which will do the same job in much smaller containers.

East of the Mississippi, lava rock are colored clinkers a silicate slag waste product from iron ore smelting, steel making blast furnaces, or silicate type slag from coal fired electrical generating plants. ( the by product of burning Coal) The clinkers, while being porous, will clog unless you have a very good pre filter system. They do not allow water to flow through them, which wastes valuable filter space. All the little nooks and crannies in the faux Lava Rock eventually become clogged with algae, mulm, sand etc. making the effectiveness the same as throwing pieces of rock into your bio filter. There is also some concern that these clinkers contain heavy metals harmful to your aquatic environment. With most homemade bio filters there is a certain redundancy built in (bigger is better) so it will take some time depending on your stocking levels and filter system, for the lava rock bio filter to lose it's effectiveness.

Lava rock is inexpensive to replace but, over the long run it is a maintenance nightmare. The sheer weight, abrasiveness and time spent cleaning, should be enough to steer you away from this product. We've cleaned many a lava rock filter and I can tell you, that trying to clean this media with anything less than a steam power washer, is an exercise in futility and will not get it back to it's original surface area. Three things should be considered listed in order of importance:

1) surface area
2) packing properties
3) void space

Red Cinder aka Lava Rock Pumice real lava rock

Surface Area and Packing Density (Properties)

While surface area measurements will give you some information, the way the media packs into a container, should also be taken into consideration. Strapping tape, for instance, is impossible to pack efficiently, whereas nylon pot scrubbies will pack much better into a container resulting in more surface area with less space.

Type of Bio-Media

Surface Area/cu.ft.

Approx. Cost/cu.ft.

Lava Rock, Clinkers

16

$   5.00

Bio Barrels

26, 33, 44, 64

$ 31.00

Biological Media Balls

96

$ 59.95

Spring Flow Pvc Shavings

60

$ 14.00

Open Cell Foam or Japanese Mats

120

$ 22.50

Bio-Pin Balls

130

$ 30.00

1/2" River Gravel

90

$ 5.00

Corallife Bio Balls

160

$ 56.00

Bio-Bale

250

$ 32.00

Nylon Pot Scrubber
Stainless Steel Scrubbers

370

420

$ 10.00-12.00

Polyethylene Beads

400

$ 90.00

Matala

Black

Green

Blue

White





62

96

124

171

   $ 30.00 cu/ft. average

Fine Sand

156 Sq. Meters/Gram

$ 5.00

Activated Carbon/Lignite

30,000 Sq. Yds./Oz.

$ 4.00/lb treats 1K Gal.

DIY

For the do-it-yourselfer, some bio media to consider in order of effectiveness and cost:
Nylon Pot Scrubbies (see picture), Plastic Strapping Tape, Springflow media and PVC Shavings.
I purposely omitted the bio-balls, bio squares and baked ceramic media, Matala Fiber and Kaldness media because of their high cost. The effectiveness of a bio filter is controlled by the surface area of the bio-media, bio bugs need a constant flow of oxygenated water, to be able to eat, breathe and reproduce. More surface area provides more beneficial bug habitat, therefore, you can substantially increase your filter surface area and lower the space needed, by using the right media.

A quick Comparison

To calculate the surface area of any bio media , dip it into a measuring tube to find its volume. Do the same with the other media and compare. More volume of solid means less surface area. More volume is just taking up valuable space.

Cleaning
I recommend cleaning the bio media only if you can see a 1/4 " build up of mulm, and then cleaning it with pond water, as chlorinated water will kill most of the bacteria and cold water will retard their growth. You should keep the filter material moist while servicing your filter, as drying will kill most of the bacteria.

If you like Math

Japanese mats have a specific surface area of about 275 m2/m3. So one mat of 2x1x0.04m is about 80 liters and has a total surface area of 22m2.
Depending on a lot of factors bacteria are able to convert between 0.2 and 1 gram ammonia per m2 surface area per day. When you calculate with 0.2 you are pretty safe.
We already calculated that the japanese mat had a surface of 22 m2, so one mat is able to convert about 4.4 gram ammonia per day.
About 2-4% of the amount of food given per day is coming back as ammonia in the pond water, depending on protein level among other things. Calculating with 4% gives a good safe margin.
So one Japanese mat was able to convert 4.4 grams ammonia per day. This 4.4 grams is 4% of the amount of food given. So total food given per day can be 110 grams per one Japanese mat.

ed. Comment---I've been using the nylon pot scrubbies for close to 35 years now. When I first started building filters, I used everything I could think of, including cut pieces of well pipe, hair curlers, plastic shotgun shell wads, strapping tape etc. Every media worked to some degree but after much trial and error, I found nylon pot scrubbies to have huge advantages:
1. They are produced for food contact, and therefore, you can be pretty sure, no harmful chemicals are used in their production.
2. After Laboratory testing they were shown to have more surface area than most media, except for some of the ceramic media i.e Siporax tm, or activated carbon. The sintered medias and A/C, however, have a clogging problem with DOC's creating a bio-film and clogging the pores, which then must be cleaned manually.
3. Nylon Pot scrubbies do not allow, unlike strapping tape or bird netting, by virtue of their construction, large gaps with no bio filtration, or compacted areas trapping dirt and debris. You get maximum, even, coverage in the smallest container possible.
4. They last for a long time--I still have 14 Year old systems running with the original nylon pot scrubbies, they lost most of their color, but look like they'll last a lot longer yet.

Chris Mountain has found a wholesale source for stainless steel scrubbers:

http://www.reliablepaper.com/Large_Stainless_Steel_Sponge_Scrubber_p/ssscrubber.htm

Thanks Chris