Q: I just got back from a business trip and after a long time once again I was curious on what was new on your blog and stumbled upon the article entitled “Just My Two Cents”. It shocked me when you gave the comparison between email@example.com (6”) koi vs 1@61cm (24”) koi. Since I started using the AFS, as you know, my pond conditions have improved significantly thus my koi have been developing well. As a result now I have 12 koi at an average size of 50cm (20”) in only a 3-ton pond. This then made me wonder whether my 31 BCB baskets are still sufficient for the load. My baskets are smaller than yours, only 25 cm (10”) in diameter and about 15 cm (6”) in height.
So far my concern is mechanical filtering but I’m still on top of the maintenance and cleaning. I feed my koi approximately 5kg (11 lbs.) per month of hi protein food (Kenkokanri Hi Silk 21) or approximately 166 gr/ (5.8 oz.) a day. This amount is actually still below the recommended feeding rate of 3-5% body weight per day. As much as I would like to add more food, I think it would do more harm than good, so I restrain myself from doing so.
The conditions of the Koi’s are healthy and quite bulky but not yet as bulky as I would like them to be. My target is to keep them until size 70cm (27.5”) if possible just to see if it is possible, since most average pond owners have small ponds like me, and if this were possible, it would be a huge boost in morale in opposition to those who say it can’t be done.
I do nothing new to the pond anymore, just continuing regular maintenance. Do you think I need to find a way to add more BCB’s to my filtering system for the target of keeping 12@70cm (27.5”) koi in my pond? Again thank you very much for your kind attention.
PS: During the Christmas and New Year Holiday season, some koi in the pond spawned. I was out of town on vacation so there was only my housekeeper left instructed to do one water change @10% per day while the koi were fasting since I left. The system held up, nothing bad happened, not even a sick koi. Water clarity restored in a couple of days. If I were there, I would have done a major water change. The AFS really did its magic, giving me extra comfort when I must leave town.
Thanks again Dr. Novak.
I thought I would share this e-mail because it brings up some good questions along with some respectable problems that face koi hobbyist with smaller ponds. Not everyone has room for a big pond but that should not stymie those that are interested in keeping Koi. Even though everyone says the “larger the better” that does not always mean it’s written in stone when using an AFS. With a conventional filtration system it could present a problem because filters must be overkill and smaller ponds lacking that versatility of room and high output pumps because the filters being governed by pump output. The AFS gives you a larger filter and the GPH pump that is needed for such smaller ponds for quicker turn over times. Larger ponds can get by with slower turn over volumes due to mass of water to fish load.
The hobbyist that sent me this e-mail is lucky, in that, in their country weather conditions are more Koi growth friendly than our weather is in the northern U.S. states. Unless you’re willing to pay for heating and high electric bills or gas bills for your pond; most Koi ponds are in a standby mode until early springtime when weather conditions permits for a normal feeding regime once again to begin. The winter months become an inhibitor for our Koi’s growth rate and it may take more years than anticipated for any larger size Koi to reach that 70cm (27”) mark compared to a country that has ideal conditions all year long.
However, that is only one component that plays a part in Koi growth rate and the size of the pond and feed rate or should I say food quantity per given day, will also be a controlling factor. Some of the better-off Koi keepers here in the U.S. will send their fish off to grow-out ponds for $500-700 USD a year to get most of their size on their fish before bringing them home to finish them off. They may gain as much as 4-6” a year in these million gallon ponds.
Twelve Koi in a 3-ton pond (705 US gals) @ 50cm (20”) is already pushing the ponds limits. It is highly recommended in books and anecdotal accounts by other hobbyists that hobbyist give at least 500-gals of water per Koi and even this number is too low and should be twice that per fish. But you will seldom see these numbers of Koi to water capacity ever being adhered to by hobbyist. This is what my article on “Just My Two Cents Worth” was all about.
Nobody sticks to the guidelines that are given with ponds or aquariums for fish to water volume stocking rates for that matter.
Nonetheless, the game changer is the AFS that the hobbyist is using on their pond and this will push those numbers of water volume per Koi mass lower. This has been proven time and time again with hobbyist and myself along with the beta testing pond in our experiments. I’m talking about water quality here not elbowroom. Though I never condone overcrowding and I’m guilty of those sins myself, I know that through proper pond husbandry and an AFS all things do not become equal comparing it to a conventional filtering system.
Even a spawning of the Koi in this 3-ton pond with very modest 10% water changes, the animals came out without any adverse health effects. This is a good sign that the AFS is doing its job and a good indicator that the hobbyist is doing their job as well.
Getting to answering the hobbyist question instead of me rambling on:
A: The question of adding more BCB’s is a legit concern because of the smaller size of 25cm X 15cm round (10”x 6”) BCB’s than the recommended size of 11”x11”x7” which will carry billions of cells more for chemical and biological processes to take place. In order to increase feeding more BCB’s will have to be added but room to add more of them seem to be the problem. It’s just too bad that you don’t have the available space to add a bigger AFS.
I have had 17 large koi in a 1200 gal (4,542.5 L) (5.1 ton) pond with four of them being 29-30” and the rest in the 16-24” range. I even show photos of them on my blog. But them my AFS is bigger than yours (8'x4'x2' deep) and my BCB’s are larger too. It’s doable to have 12 Koi @ 70cm but feeding them more without a larger filter will become the problem. The larger filter will add needed volume to your waters mass, too. Your mechanical prefilter will have to be top notch. If you can accomplish this, you will be the envy of other Koi keepers in your country.
Here is an old photo of the Koi I was talking about in my pond. The smallest one is16" in the background and the rest in the foreground are 20" and larger. So, it is doable to have large Koi in a small pond using an AFS.
Brian Woodcock in the UK is a prime example of how well his Koi are doing in his pond that should have far less Koi in it. He is already thinking of modifying his AFS this spring once again to a MK II AFS filter (1). I can’t wait to see his new modifications to his Mk II. It should make for some very interesting reading and photos this summer.
(1) [ED: I do not know what a MK II AFS filter modification is as of yet so we will see when Brian’s done with his filter. I know that I have found some really nice 1 x 1” square black PVC pipes at Lowes to place on the bottom of my filter. These hollow square pipes will lift the BCB’s off the filters bottom and make it easier for filter cleaning. This will be my project for this year and I will take photos to show the details. Being that these will already be black and square, it will make installation easier with less prep time involved.]