Hi, yes we raise koi and have a 5,000 gallon pond. I upgraded to a 6000 gallon aqua ultra Ultima 2 bead filter, inline with a 54 watt inline UV sterlizizer. You should still backlash your filter ONCE a WEEK for fish health but you never have to actually clean this type of filter, NEVER! Backlash is so simple just hook a hose to exit port and turn to backlash, then rinse, it's as simple as that! I highly recommend this type off filter. It sure saves a lot of heart ache and time. I went 1,000 gallons over with my filtration. Running on a 6000 gallon per hour Sequence pump. The filter is the heart of the pond. Make sure your pump is matched to your filtration. I recommend Ultima2 because they won't gum up like other bead filters. For what your getting its a reasonable price. If your a serious pond keeper this might be just what your looking for. We did our installation by ourself. No problem And I love mine, waters crystal clear! Make sure to install a UV sterlizizer because it's a God send, it keeps algae down and it's wonderful. If you have any questions I'll be happy to answer them. I wish you the best!

Thanks - I'm sure I'll need to upgrade the pump gpm. I've not used a UV Sterilizer for the last 6-8 years, but the water hasn't been Crystal clear, but okay with the one inline pressure filter. I was going to make a skippy, but didn't think I'd get as involved as I have and when I did the install on the 1000G pond my small reformed was already installed and the system is too close to the corner of the yard for any rooom for a skippy unless it is totaly above ground and not sure "you know who" would be pleased. But, overall, weve enjoyed the pond system which is a little 35G preformed that now has plansts and acts as a skippy type filter, the preformed of around a 100G or so and the last addition which I guess is around a 1000G. It's quite hard to get rid of the Kioi as again, "you know who" names them and each year wants to get 2 small ones for the middle pond so the large pond is grossly overstocked. Bottom line I guess is that you can neve hve too much filtration. Part of my point is that each year, age keeps taking a bit of the energy and hopefuly each year I can do something to reduce maintenance activities.
again, thanks.