Do It Yourself Pond Filter

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In recent weeks we’ve talked a lot about pond filters and how they can be very important to helping keep a pond clean, clear, and free of algae.

There is no question that one of the best types of filters for this task is the biological filter, which uses beneficial bacteria to break down and assimilate all organic elements found in the pond. This includes pond algae of course but other materials like small leaf debris, fish waste, and pretty much any other “organic” material that makes it’s way into the pond in one way or another.

A well running bio-filter can do wonders for a pond and it can help keep algae under control as well as so many other things. Namely…your sanity…as a true bio-filter is not meant to be cleaned. The type of filter discussed in the video below actually ran for a number of years before the owner decided maybe it was time to clean it out. And they admitted it was a mistake to do so since it had worked well throughout that time, after the initial period of adjustment after the installation.

This is a perfect, simple, DIY project that anyone can do. The system is designed in a way that is scalable to many pond sizes and demands. So if you’re looking for a pond project to take on this spring, maybe a DIY filter will be entertaining for you, and it might even save a few bucks too.

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23 thoughts on “Do It Yourself Pond Filter”

  1. I plan to try this, but my problem is also the string alge. Does this help with this? If not, how do you keep it in control and not interfere with this type filter? Thank you!

  2. Hi Sarah,
    While it’s true that string algae won’t get passed through the filter system in the same way that blue-green algae might, the bio-filter can help control it.

    The key here is what the filter does with the organic nutrients in the water. All types of algae feed on and are supported by nutrients. Bacteria go to work in the filter, and if they have places to colonize, in the pond itself and reduce these nutrient levels.

    The bacteria also helps process problematic elements through the nitrification cycle that turns dangerous things like ammonia and nitrites into usable and safe nitrates as they break down whatever organics are present in the pond and in the filter.

    So in essence what makes this all work is the bacteria, and not so much the filter. The filter does catch and actually filter the water, but it’s the bacteria that does the real work, both inside and outside the filter itself.

    One other key point I forgot to mention in the article and the video. A bio-filter and the flow through it should ideally be done 24/7. The bacteria colony needs good oxygen levels to thrive. If you have good water flow and circulation, oxygen is gathered at the ponds surface and is actively circulated through the pond and the filter system…so you don’t want to turn this flow off unless it’s absolutely necessary. Doing so will often dramatically reduce the established bacteria in the filter.

    On our website you’ll see a product for small ponds called the 2500 system. This small dispenser and the packets that go in it serve as a “bacteria colony” that you put in the pond itself. This is a unique system in that it time releases bacteria on a continuous basis for 30 days before needing to be recharged.

    The 2500 system is what I use to not only establish or prime a colony of bacteria in a bio-filter, it’s also useful if I happen to see some algae forming in the pond itself. I can run with the filter for the most part, but if I need to, I can charge the pond directly with bacteria and often this will eliminate string algae or green water issues in a safe and effective fashion.

    I hope this helps answer your question somewhat.

    Best wishes,

  3. I am interested in this also. I’m not sure what drives the circulation. Do you need a pump to bring the water in and circulate it?

  4. Hi Linda,
    You’re correct. You’ll need a pump of some type to circulate the water. There are a number of different kinds available from submersible pumps which sit in the pond to external ones that would be land based, they are all designed to circulate the water through out the pond’s filter system(s).

    I’m not an expert on pumps by any means but I’ll try to do an article in a few weeks that covers some basics when choosing one.

    The main thing you need to keep in mind with any mechanical item in a pond is to make sure you get one big enough, or powerful enough for the pond’s water volume, and the demands put on it…such as a waterfalls system, or flow rate recommendations for filtration systems if they are listed.

  5. Last year mid season I build a box out of land scape timber and a piece of liner letting the water flow down through the filter media devided by a piece of plexi glass held by cilicone 1″ from the bottom that would rise to the over flow back into the pond. The temperature was not bad so it keep the pond clear a 1800 gal pond.
    I was so inpressed with your skippy filter that I have all ready purchased the products you listed.
    Let you know how it works for me, I am in full son and have had lots of problems with alage. I decided to use the 100 gal rubber made tank for extra measure!

    Thank you,

  6. Thank you Mark for this information, will definately try this, we are opening the pond this weekend, so it will give us a project. we can add it as an extra David

  7. If you need more than one filter are two pumps required? My pond is about 7500 to 8000 gallons and would need at least two of these. Thanks for all the great tips!

  8. Hi Mark:

    I built one of Skippy’s filters several years ago for 100,000 swimming pond, using the 300 gal. Rubbermaid tank.

    Here is a few things I discovered along the way. First it works great. I moved mine after two years and when I drained it I had a good two inches of sludge in the bottom.

    Secondly, I bought a lot of scrubber pads off E-Bay for little money to use as filtration. I also picked up small scrubbing pads at Sam’s Club to help fill out the thing.

    My pump and filter pushes 6,000 to 7,000 gallons an hour through the system. The water coming out of the outflow is as clean looking as can be.

    I still have to fight algae, but this is because my pond is too large for my filter.

    You cannot beat this filter though for helping to keep things clean.

    John Beane

  9. John…thanks for the info and congratulations on putting a good system together.

    Snowman…I would say if your pump system is more than adequate for your pond size you should be ok. We always suggest overdoing it a bit with this anyway. The filters as described are not really under any pressure but as always, you need to take into account the total volume of the pond and the entire system design and use this to consider the pump size.

  10. Doesn’t help in my pond I have string alge in it. I have the skippy filter for the last two year but my pond is way big 26,000. IF ANYONE can help me with that please let me know.

  11. Hi Debby,
    Thanks for the note. Based on your gallons size I’m taking a guess that you’re way under filtered if you only have one skippy working at it. It would likely take a series of them to do any justice to a pond of that size.

    Your best bets, other than adding more filtration would be to supplement with beneficial bacteria, in the right amount and frequency, add plants, particularly floaters that can block light and outcompete some of that algae for support.

    You might research things like barley straw which works on algae sometimes and keep working on trying to balance the pond out as best you can. Oh and do your best to keep organic material from going into the pond. Things like leaves, grass clippings, anything that can break down and feed more algae growth needs to be removed if possible.

    Hope this helps.

  12. We have a 2000 gal. capacity natural pond that is spring fed. There is no liner. There are bolders on the bottom. The water is constantly flowing in from the spring and the overflow goes out a pipe in the pond. Will this system work for us? Thanks, Mary

  13. Hi Mary,
    It probably could. Much I think would depend on how fast the flow through is in the pond. If, for the most part, the water remains in the pond body for some time, then the filter might be of benefit.

    Of course the filter is part of a system that involves a pump which drives the water into the filter system. The output from the filter is just like an overflow pipe, which directs water back into the pond.

    One thing you might want to try first is simply some bacteria supplementation in the pond body itself. If there are enough areas in the pond for bacteria to set up some colonies, then you may not need the filter system. If you have some algae issues, it might be worth some experimentation to see.

  14. You recommend using scrubber pads for filter media in the skippy filters, but you did not indicate whether you use the fine medium or coarse grade. Which do you use? If I were to implement scrubber pads in a 55 gal barrel filter, does it make sense to use fine scrubbers on the bottom of the stack for mechanical filtration and follow with e.g. medium scrubber pads?


  15. Hi Eric

    I would use the coarse grade pads as those have a little bit bigger cavities to hold the bacteria. I think your idea is worth a try in a mixture if you like and worth experimentation. Please post your findings if you do this and we’ll add it to the commentary which might help others down the road.

    Thanks very much!

  16. Hello Mark.

    Thank you so much for this upload. I have been scouring websites for diagrams, tutorials or just anything that could explain how to make a bio-filter without being too obtuse in terminology or lacking explanations as to why this feature is important over another. Again. Thank you!!

    This video is helping me plan out the bio-filter I am using for my red-ear sliders even. I am planning to make an indoor pond for them with a 55-120gal tank. (55 for now as they’re quite small.)

    I did have a question about priming the pond. During this stage are we not supposed to have creatures in the water or is this time period ok? My turtles are messy creatures and 1-2 months is a long time to wait for the system to clean it’s self. Is it better to have that process pass and then add the amphibious creatures?

    Thanks again.

  17. Hi Mimi,
    You can add bacteria to the pond at any time really, which is the way you prime this filter. The regular use of beneficial bacteria will help keep the pond cleaner overall…and prime the filter…all good stuff.

    Something like our small pond 2500 system would work well for this as would any good bacteria product.

    Take care!

  18. I too am using a biofilter for my 3 ponds. I
    have an algae problem but from what I have read
    i seem to be on target for my algae growth. The thing I never hear mention of is whether the algae problem is being exacerbated by the use of the fertilizer tablets in the water lilies. If my pond is producing too much algae, do I need to use fertilizer to get the desired lily blooms I am looking for? If that is the case I will gladly curtail the use of the fertilizer tablets. My test strips show that I am in normal range for all testing. But I still can’t see my fish.

  19. Hi Guhru,
    You make a very good point about fertilizing desirable plants.

    Normally I think if this is done in pots, you would have less of an influence but there still could be some seepage of the nutrients I suppose.

    Overall though my thinking would be that as long as this is not overdone, the plants themselves would probably use up most of the nutrients before the algae would have a chance to do so.

    I commend you for thinking and looking for root issues though…this will help you effectively combat an algae problem more than anything else.


  20. Our pond is about 3500 gal. Having viewed your excellent video I am wondering which size container we will need and where to purchase one. I checked online and found nothing over 95 gal. Also, how do get the return water back in the pond without a return hose from the flange? Another thing mention somewhere is a stock container, I think, what is this and where does one find this?
    After hooking up the filter when and where do you put the biological chemicals? This system does not go in the pond I am assuming but what do you use to cover the system?

  21. Hi Jessie,
    A 100 gallon container will work up to about 3,000 gallons. A 150 gallon container will cover about 4,500 gallons. You might find these at garden centers, feed stores, or you might search online for them. The return water can be routed through a hose if you like, some people just let the water come out and go down a water fall area, stream bed, etc. You could basically come up with just about anything.

    The biologicals can be added directly to the pond and as they circulate through everything, they’ll prime the filter up. You’re right as well in that the filter doesn’t go in the pond but sits outside of it and it can be covered with a sheet of plywood or similar material and you could plants, rocks, etc over it to decorate.

    Hope this helps a bit.

  22. Are there any preparations that must be done to the biofilter for winter, to avoid the effects of water freezing and expanding in the filter and possibly damaging the pvc?

    I had excellent results using this filter. In two-three days it cleared my pond up in the spring. I used blue furnace filter pads cut up, as I had a limited budget. On top of those I added a layer of quilt polyester batting. I don’t think I will use the quilt batting again because at the end of the season it basically disintegrated.

    I also added water lilies-but they didn’t survive-I have a partially shaded pond- and three Goldfish which are huge now, and I have Anacharis which did well. I brought the Anacharis inside for the winter-I put them in a fish tank. I have a pond heater going now, aerators, and I also left the Goldfish in the pond for the winter.

    During the summer I only fed the Goldfish once or twice a week.

    Also, how do you keep the scrubber pads from floating? Another grate on top?

  23. Hi Candy…I would drain the filter completely if you’re shutting down the water flow and all that. A biofilter won’t be useful in cold weather anyway. But it’s probably best to just drain it, and clean it out, basically starting fresh each spring. On the pads, it probably depends on what you use, as some might float and some would probably stay down, but you could certainly put something like another grate on them to hold in place. No issues with that at all.

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