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Thread: Under Gravel pond filter questions

  1. #1
    Tosai
    Join Date
    Jul
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    15

    Under Gravel pond filter questions



    Had my pond 1500 gal +- installed this past June for my (2) 20" koi and (7) goldfish a5 years old . The old Concrete pond can be see to the left. I used an installer with 20 years of experience. He uses under-gravel systems with success, though according to the installer they have to be cleaned every 4-5 years ( I think more like every year). They installed an network of pvc perforated pipes connected to a pump which discharges the water near the skimmer, the stones covering the under-gravel pump are visible in the photograph. This will be the first time I will be leaving my 20" / 18 year koi out. They are now to large to safely move and house. Plan on taking the some of the smaller goldfish in.


    My research indicates pros and cons with this type of filtration. I plan on adding a canister and "retro" bottom drain in the Spring, possibly abandoning the gravel system.

    I am getting concerned about the up-coming winter( Southern NY state) . Shutting down the system will possibly discharge trapped gasses in to the pond, leaving it on will affect the water temperature. Not sure what to do!
    I do plan on using aeration and a deicer.


    Doug
    Attached Thumbnails Attached Thumbnails Under Gravel pond filter questions-img_8533.jpg   Under Gravel pond filter questions-img_8532.jpg  

  2. #2
    Honmei ricshaw's Avatar
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    Mar 2010
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    Southern California
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    I have had Koi ponds for over 35 years. My first pond had an in-pond under gravel filter. My first aquarium had an under gravel filter. My current aquarium and Koi ponds do not have under gravel filters. The reason is under gravel filters are very old school and there are much better biological filter options. Any pond installer, with knowledge about Koi ponds, would not recommend cleaning an under gravel filter every 4 - 5 years. When I had a pond with an under gravel filter, after the second year, I had to physically remove and wash the gravel EVERY YEAR because the water flow would channel and anaerobic pockets would form in the gravel.

  3. #3
    Daihonmei MikeM's Avatar
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    Dec 2003
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    Orlando, Florida
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    11,128
    In regard to over-wintering koi in your area of New York, I'd suggest contacting the Saugerties Chapter of Mid-Atlantic Koi Club. They will have knowledge based on experience in your climate.

  4. #4
    Fry
    Join Date
    Aug
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    8
    I hope you don't have raccoons in the area. They will love sitting on the rocks and going fishing in the shallows. I have had them bail the pond down to a level they can fish. As far as bottom filtration: many I know have removed the gravel as too many sick fish.

  5. #5
    Jumbo RobF's Avatar
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    Jan 2009
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    Orlando, FL
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    Doug, That is a nice water feature that you have added to your place. I say water feature instead of koi pond to distinguish between the purposes. The submerged shelf will be nice for plants but is a staging area for predators. Many of us started out with a similar small pond (or even smaller and less filtered). When I had a pond of that size I made a woven wire frame that I put over the pond each night to keep out the raccoons (after losing many goldfish). I think I see such an arrangement over the old concrete pond. If you don’t feed much it will help to keep the pond clean and you don’t want particularly big fish anyway. If you last a couple of years, and get with a club, and go to a show you will see that the grass in your yard is taking up a lot of pond space.

  6. #6
    Tosai
    Join Date
    Jul
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    15
    Hey Rob,

    Thanks for you impute. The photographs are pre stocking. I do have Raccoons in matter of fact I saw 4 babies the other night. I did have issues with the old pond years ago. I found my goldfish partially eaten. The shelf in the new pond is 18" below the surface. The gravel area is 36" deep. In addition I now have netting over the top. I believe raccoons do not like deep water and should, so far have avoided the pond. More concerned about wild mink and birds. Have no plans to add more fish Just happy to give my guys space to swim.
    Just do not know if I should turn off the under grave filter for the winter, with concerns of the crap below gassing out. Leaving it on means a water temp issue.

    The guy I used has been installing ponds like this for over 20 years. Reason I choose him. In addition I have ground water issues making a bottom drain impossible. The other installers were planning on a skimmer and filter at the water fall only, no bottom drain.

  7. #7
    Tosai
    Join Date
    Jul
    Posts
    15
    Thanks Mike,

    I see there are two clubs, one is the tri-state Koi club and other is the Mid Atlantic club. Not sure which one. Saugerties is about 90 min north of me. Finding that there seems to be a "void" in my area. Everything is North or South of me. Thinking I would have to join to post a question. I may do so, sounds interesting.
    I know that people in my area keep there koi out, however last years sever winter did take its toll. I have been taking my koi inside in October and return them to the pond in May. This year they will be staying out due to there size and lack of space inside. I will be keeping a close eye on them. You are lucky that you live down south.


    Doug

  8. #8
    Nisai
    Join Date
    Oct 2004
    Location
    Orange Park, Florida, U.S.A
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    81
    Quote Originally Posted by RobF View Post
    If you last a couple of years, and get with a club, and go to a show you will see that the grass in your yard is taking up a lot of pond space.
    I’m not sure if I ever read a funnier (or more true) statement than what Rob has written! In 1995, when I began thinking about putting koi into my existing backyard swimming pool, I had NO IDEA of where to begin, although the pool was already big enough to be occupying most of the available yard space, so that was not a consideration. I did ask a bunch of questions, but, unfortunately, mostly not to the right people. One landscape company, which billed itself as koi “experts”, told me “All you need is 18 inches of water – 10 feet deep is MUCH too deep and you will not be able to maintain it that deep as a koi pond. What you need to do is to fill the pool up with gravel, leaving only the 18 inches of water, then add your koi. We’ll be happy to sell you the gravel.” Thank goodness I didn’t do that! In short order, it would be nothing more than a septic tank! Another owner of a tropical fish store told me to “take out the innards of your existing filters and then add big, honking snails to keep the water clean. I’ll sell you the snails.” I didn’t do that, either – finding out later that snails are a common vector for some really bad koi parasites! And so on . . .

    Finding one or more koi clubs (and people who have “been there, done that”) is some of the best advice anyone can be given.

    S. Stone

  9. #9
    Tosai
    Join Date
    Jul
    Posts
    15
    I hear you. However my original intention was to build a larger home for my 2 koi and gold fish. I am in my 60's and got tired of lugging these guys in and out. I wanted a small pond ( cost and space) and did not want to chew up my yard. What you do not see is there is about 6' of grass between the pond, the deck and some large trees. My entire lot has drainage issues (clay) . This area also floods during heavy rain storms the reason for lifting the pond up 12".

    I have had gold fish for 40 years or so some of the current ones are decedents of the original. In the winter I use two tanks, both with canister filters external filters. I do the weekly water change, never had an issue until the canisters failed an leaked 20+ gals of water on the floor. Said this is it, these guys have to go outside. Thus the pond.
    I am aware of the down side of the under gravel system ( would never use it in a tank). I had a horrible time getting someone. Most wanted to install a 10,000 gal "lake"costing over 20k. The guy I choose has a good reputation and surprisingly advertises his under gravel system as biological. The problem now is to get him or someone else to remove the fish and the gravel, cannot install a bottom drain.

    By the way. I am semi retired and have limited funds. I built what I can afford and with the space I had, along with my age are factors that need to be considered.
    I attached a current view of the pond with the fish. I am afraid the reflection and netting obscure the picture

    Doug
    Attached Thumbnails Attached Thumbnails Under Gravel pond filter questions-img_8748.jpg  

  10. #10
    Nisai
    Join Date
    Oct 2004
    Location
    Orange Park, Florida, U.S.A
    Posts
    81
    Doug:

    I didn’t mean my response as any kind of criticism, merely memory and commiseration of someone who has been on the same journey, only maybe meeting with different challenges. (It has been called “koi crazy”.) Even though I am still working full-time, I, too, am getting “up there” in years (will be 71 years in less than two months!) and face more and more problems in handling many of the larger koi, or with other usual pond maintenance jobs.

    The person you chose to build your pond obviously has a sense of aesthetics and it appears that he did a good job in doing the construction. The outcome is really beautiful! As to the bottom drain, if you physically have enough room in the pond, you might investigate a “retro” drain that is attached to your filter system with external piping. It looks sort of like a large turtle, if you see it advertised in many of the koi publications.

    Shirley

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