Biofilter media

cweathersbyMay 17, 2010

I was out of town last week and my biofilter clogged up which resulted in over half of the water leaking out of the pond. Luckily, no fish were harmed! The pond lost at least 3' - but it's around 4-5' deep.

For the first time in 4 years I emptied the biofilter completely and tried to figure out where the problem was.

I had to take everything out and throw it away. Wasn't a completed set up to begin with. It's a 300 gallon rubbermaid tub, the pump pushes the water from the big bottom pond's bottom drain and it vortexes in the bottom of the rubbermaid biofilter and exits the top into a 4" pipe that feeds the waterfall.

The problem wasn't so much in the set up as it was in the media used in it. I had quilt batting in mesh bags and plastic soft drink lids in mesh bags. AND I put various potted bog plants into the top of the biofilter which had completely jumped out of their pots and rooted into everything. The congestion of their roots is what caused the problem I think.

The plants are all out, the media is all out, the tons of muck are out, and it's just an empty tub with water running through it right now.

I'm going to put a grate over the bottom (not that plastic ceiling stuff which breaks too easily which is one reason the setup wasn't perfect to begin with- I tried the plastic stuff, it broke, and I just set the bags directly on the bottom). This grate will allow the vortex to actually vortex... something it's never done before.

I would like to use polypropylene strapping in the middle. Above the grate but below the overflow into the 4" pipe.

I'll top it off with another grate to ensure that none of the strapping goes down into the waterfall which would be a mess if it got sucked into the bottom drains and pump.

Looking for strapping material around town- Only thing I've found was polypropylene baler twine. They sell it in 10,000 foot sections.

Will that work? It doesn't have the dimples. BUT it does have lots of surface area.

Thanks for your help,


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Sorry the pictures aren't clear. My cell phone doesn't take good ones.

    Bookmark   May 17, 2010 at 3:26PM
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sleeplessinftwayne(z4-5 IND)

It should work but it would work better if the strands were loosened somehow. That sounds like an awful lot of work.

    Bookmark   May 17, 2010 at 3:34PM
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ccoombs1(7B SC)

I actually know someone who used that stuff. He braided it into big thick ropes. It worked fine, but also trapped an awful lot of solids and clogged and was somewhat hard to clean. Bio should not be exposed to that much debris if it is to work well. It will work....but there are better things out there. Have you looked at plastic bird netting? I wad sheets of bird netting into big chunks and pack it into my barrel filters and it works wonderfully well. It never breaks down and is not hard to clean.

    Bookmark   May 18, 2010 at 6:25AM
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I was thinking of putting the baler twine into bird netting to help keeping it in place. What would the difference be between this stuff and the bird netting itself? Why would the baler twine catch more solids?

I was reading that some forum members say the polypropylene strapping is the best and cheapest biofilter media - so I'm wondering which media would be considered better? And why?

Does anyone know where I can get the strapping? I've checked Home Depot and I've checked a place called The Shipping Store. No luck. They've got it online but it's expensive to ship.

    Bookmark   May 18, 2010 at 10:59AM
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ccoombs1(7B SC)

The bailer twine is made up of very thin threads. It packs together too tightly to allow water to flow through it well enough. The fibers are so small that it will clog, like a sand filter clogs. It also may break down over time, but I am not sure about that. Bird netting can't be packed as tightly. Water can circulate around it, which is what's needed for bio-conversion. If the water can't easily circulate around your bio media, the bacteria won't grow and the filter won't work. Strapping material works pretty well, but the surface of some strapping is very smooth and bacteria has a harder time establishing on a very smooth surface. Bird netting is inexpensive, has a good texture and has good surface area. It's not as good as commercial bio-media (such as bio balls), but it still makes an excellent bio media that can be easily cleaned. When I need to clean the filter, I fill a barrel with pond water and gently shake the wads of bird netting in the water to rinse the debris off withough disturbing the bacteria.

    Bookmark   May 18, 2010 at 12:28PM
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Well dang.
Here I was thinking that I'd found the perfect cheapskate biofilter media.

With the bird netting - what I've looked at so far was 17 bucks a pop. I'm guessing it would take a whole bunch - maybe 10 or more? to fill a 300 gallon skippy?

Floor scrubber pads - what do you guys think of these? I may put some on the top (I know on the bottom would be better but I can reach the top to clean if they get clogged). The big commercial ones - which size fits best into a skippy?

    Bookmark   May 18, 2010 at 12:56PM
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ccoombs1(7B SC)

Look on line for bird is usually pretty cheap. Floor scrubbing pads work pretty well for mechaincal filtration but not so great for bio. And some have anti-bacterial or anti-fungal products in them that are not safe for ponds. I have heard of many cases where they worked just fine with no problems at all, but also heard of two cases where the fish died as a result of some chemicals in the scrubber pads. Since they are not designed for fish use and SOME have problems, I'd be leary of them.

    Bookmark   May 18, 2010 at 1:00PM
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shelley_t(z5 IL)


First of all I love you! ...and all the rest of you "pond-ers on the cheap"! What great DIY stuff you've put together! Mine is similar, but just plastic scouring pads and lava rock.

I wonder what you would think about a plastic grate. Similar to milk crates... or old milk crates for that matter. I needed something similar, but wider for my chicken house floor. I found kennel flooring and cut it to size. I think it came in 4 x 6 sheets at Farm and Fleet.

I was thinking you could set it on top of plastic landscape fabric to discourage the roots from wiggling down into your media and the weight of the grate would keep the lower things from settling.

Good luck!

    Bookmark   May 18, 2010 at 1:20PM
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hardin(7 SE OK)

In my filterfalls, I have 2 large media bags. One is full of dishwashing scrubbers and the other has a few bio-balls and lots of bath scrubbies. There is also the filter that sets in the bottom of the filterfalls. So far they are working very well and easy to clean. As said above, just rinse with pond water in a separate bucket. I only do one, leaving the other, alternating each time, so the bacteria can keep up.

    Bookmark   May 19, 2010 at 8:49PM
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A word about bird netting -
Put 2 big ones in there and the frogs and snakes get caught in it and die.
Pretty sure a dead rotting frog isn't good for my pond..
It was the worst thing I've ever smelled that I had to actually TOUCH!
Right now I've got the big floor polishing pads in there on top of the bird netting in hopes of keeping the pond critters out of it. BUT the frogs hide under the polishing pads so I don't know how much good it's doing.
How do you guys avoid this?

    Bookmark   July 16, 2010 at 2:39PM
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Just about anything will work as a "biomedia" - plastic strapping, bioballs, springflo, knives/forks/spoons from a church bazaar. What they are made of is essentially immaterial as long as the material does not have a bio-toxic surface (nothing mentioned in the above posts falls under that category). PVC, Polypropylene, Polyethylene - just about all the plastics you can name will work just fine. They don't generally break down as long as they are kept submerged - the primary culprits for causing them to break down are ozone and the UV components associated with sunlight (Nylon is notorious in this respect). The fine strands will not really participated in the effective surface area of your bio-media since they will rapidly clog with bacteria. For the same reason, lava stones also tend not to offer the surface area you may want. Floor polishing pads or similar filter media will work...for awhile; then, they too will become clogged over time and need to be cleaned. I prefer anything that is lightweight (your use of a top grid to keep it submerged then becomes essential), that is fairly open (I'm lazy and don't want to clean it more than twice in the season); and of course....I like it CHEAP!. All of the plastics, over the years, will tend to become a bit brittle. Hope this helps.

    Bookmark   July 16, 2010 at 6:24PM
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garyfla_gw(10 Florida)

have used drinking straws for many years . Can't clog, doesn't grow algae ,easily cleaned . You can get 200 for a buck at the dollar stores I cut each straw into 4 pieces leavea almost no gaps . gary

    Bookmark   July 18, 2010 at 4:52AM
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Try they have strapping.
The baler twine sounds interesting. I'm always looking for better bio.

    Bookmark   July 21, 2010 at 10:18PM
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woeisme(z7b NC)

Try eBay, I got 7500' 1/2 strapping for about $37 shipping included. That should be enough for a 300G stock tank. Use a mechanical pre-filter like Mattala mats or Even just the egg crate found in the drop ceiling section of Lowes or H.D. Some people even use Non-fiberglass furnace filters. Bird netting is great to hold the strapping together. Be advised that the strapping does not sink. You will need something to keep it in place under your outlet of the stocktank or it could get sucked in. A pipe with holes in it or some sort of strainer basket devise.

Here is a link that might be useful: The Pond Forum

    Bookmark   July 22, 2010 at 2:45PM
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I love cheap/free/scrounged, etc. I never thought of using bird netting/shade cloth in a bio filter, but---- I'm just two blocks from a big greenhouse operation, think I'll talk to him and see what he does with his used, scrape, throw away shade cloth.

Thanks to all for making the wheels turn!
PS> is there anybody out there in south central Oklahoma?

    Bookmark   July 23, 2010 at 10:54PM
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Not Oklahoma, but Texarkana if you are ever close.

    Bookmark   July 23, 2010 at 11:34PM
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I have a 50 gal drum as a biofilter. Used the light grate cut in a circle sitting on a frame made from pvc pipe. My water enters from the bottom in a 2" pipe which has a 90 on either end so the water swirls in the barrel. The grate is supported by the pvc frame and the 2" pipe and the media sits on top of this. I use springflo in one mesh bag and bird netting/scrubblies and media from my indoor pond in another laundry bag. The laundry bags are cheap but strong and I suppose some bacteria grows on them as well as are cloth. Use the bags so that I can shake them out in the barrel then put in another container of pond water while I empty the barrel. I have one black matala mat on the top of the media as the bags tend to float.

Lava rock is heavy to lift out of a container for cleaning. I like the springflo have been using the same stuff for 6 years now but I don't run my pond all year. Bird netting or even plastic trellis netting works okay.

    Bookmark   July 24, 2010 at 12:27AM
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