I agree. Anything you buy at big box Lowes/HD will be maintenance-heavy, insufficient and in both the short and the long run, cost you more.
Koi still make koi poop whether they are in a pond or a QT. You need a mechanical way to remove the solids and something in/on which to grow the good bacteria to convert harmful substances to safe. For something QT size, it’s easy to do a DIY filter.
Memorize this bon mot: filter manufacturers lie like a rug when they tell you the size of the pond they will ‘clean’. (Well let me be more gracious: mfgs can’t possibly know how many koi you have or how large they are or how much you feed them.)
Pressurized filters like they sell at Lowes/HD are a PITA to clean. Koi poop does not backwash out of sponge pads, particularly if you are feeding high-protein which tends to be a bit greasy; you have to take the filter apart and hand wash in a bucket of pond water. All this taking apart of the filter weakens the clamps and shortens the life of the unit. When a task is a pain, it is all too easy to put it off, have water quality plummet and find blood-streaked, curled fins from nitrite poisoning. When I had five <8”-10” new koi in there, I had to clean the blasted thing daily to keep up the water quality. I don’t have time for that crap – literally and figuratively.
I made a good one for a Rubbermaid 150gallon stocktank with a 32 gallon trash can and K1 -- and I am not mechanically inclined in the slightest. The beauty of this is that I clean it in under 3 minutes by just opening a gate valve. Now I am upgrading to a 300 gallon stocktank with two 32 gallon trash cans -- one a vortex and one a moving bed. (I keep two 12" comets in there at all times to keep filter cycled.)
You can do it!
