What a wonderful wake up response! LOL That short posting really meant alot to your seriousness to this topic. Joined a pond club, GOOD FOR YOU! very smart move there! You'll not only be surprised at how much information can be gained there but you'll also find that there are plenty of folks that don't mind lending a helping hand in order to help you maintain a healthy pond for your fish. Second plus, I think you realised very quickly that there is a problem and a great way to go about trying to minimise it. Yes getting some of those fish out and reducing the #'s will help greatly! I hate to tell someone to get rid of fish that they have had for a long time but in the interest of of good quality water management this is a really good choice. Hopefully you'll find them a great home where someone else can enjoy them and while someone is helping you advance you help another advance. Your pond size is the next thing we need to discuss, 2000 gallons is good for about 200" of fish give or take. Of course it would work a lot better with 200" of small 4-5" fish than 200" of 24" fish but this is a standard guideline for aquariums and most ponds. Example, A 30" Koi in a 500 gallon pond, That's tight quarters for a adult koi, But it can live and survive in that, 4-5 adults in 2000 gallons. now there are those that will push that to the max. with really good filtration and good water quality I would say the possibilities are there for successfully keeping maybe 6-7 adults if you maintain pristine conditions. So you still have alot of fish in a small pond, even though 2000 gallons is considered fairly large for a garden pond to some this is small in reality due to the size Koi can grow, and the amount of waste them suckers can put out. I have about 22-24 assorted Koi, and comets in a 2500 gallon pond, largest is 18" but 75% of my fish are under 6-8" I'm looking at culling at least 4 probably 6 fish in the very near future. Total inches in my pond are 180-190 inches, But I do water changes of 10% weekly and religiously, My filters are not small, Just to give you an idea, I run close to 30 gallons of bio balls, two 4' round, x 1" think matala pads, and once filter through that then my water goes through a 300 gallon pond stocked 100% with plants, I also use a bog filter and prefilters before the water is filtered. the pre-filters which are made of matala also are cleaned once a day everyday including dead of winter, and like right now when the fish are active and feeding well, three times a day is normally what is needed. I back flush the filter once a week and I monitor water quality 1 time a day most days but about twice a week I do check twice once in the morning once in the evening to make sure afternoon temps aren't getting spikes out of my comfort range. I also have other places to keep fish if a problem occurs, Plus I am in the planning stages of a far bigger pond and filter for my Koi just as you.
So long story short, Reduce the fish load as much as you can, read up on DYI and talk to local ponders see what they are doing and what is working, and if your going to try and keep a heavy load of fish in your pond, Forget small filter, think big and effective. remember, Big and effective can be a little costly, But taking into consideration that a small filter that would do you almost no good is $300 spending another $1,$2 or $300 and making one that has 10X the filtering capacity and will last you and your fish for many years may be well worth the effort and money well spent. If you look in the DYI section at the filter I just built for my 300 gallon pond, TRASH MASTER total cost even after modifications about $100 not including pump. Very capable of maintaining three adult Koi I feel certain if the pond was bigger. Has a way to backflush, no UV light at all and it's in 100% sunlight with crystal clear water. If you make a Vortex tank first to separate solids and then two 55 gallon Bio-filters tied in together You would have a extremely effective filter, that would be easy to maintain, comfortably keep 6-7 koi in your 2000 gallon pond and cost you about the same maybe a little more than that filter you just bid on and retracted. Big and bulky yes, not easy to hide kind of yes, you have to build yes, effective and easy to build and maintain excellent, water quality far better and Koi will look better, feel better and stay healthier.
1 hour post, I think that's enough for this one! LOL
So that's a start anyhow. 
