| You guys make me feel like I am mistreating my koi. My only pond with anything resembling a constant feeding regiment is about 20,000 gallons with about 25 fish. My best guess is that there are:
3 @ 6 kg
5 @ 4 kg
8 @ 2 kg
9 @ 0.3 kg
That's a total biomass of about 57 kg (125 lbs.)
They are fed 6 handfuls of feed twice each day. A handful is about 33 grams so they get about 400 grams (<1 lb) of feed per day. That's only 0.7% body weight per day. They also get about 4 liters of fresh seaweed 3-4 times per week. The amount was derived empirically based on the amount the fish seemed to want to eat. I have no idea what the dry weight of the seaweed is but doubt that it accounts for more than 25 grams per day - so I am up to 0.75% per day.
They get the first ration in the morning between 7:30 and 9:00. However, they seldom start eating before 9:30. They get the second ration in the afternoon between 3:00 and 5:00 but do not eat a bite until 5:30 - you can almost set your watch by it. I have to use a feeding ring to keep the feed from going down the skimmer while the fish think about it. There is nothing resembling a feeding frenzy. Some will do the grab-and-splash routine, but overall it is always very leisurely. It is usually about 45 minutes from the time the first fish takes the first bite until all the feed is consumed.
I feed Nelson's Silver Cup salmon feed - 48% protein and 11-15% fat. Yeah, I know you guys are really gagging now. Every once in a while, I will splurge and buy a bag of cheap koi feed (Nelson's, labeled for the local distributor) - 35% protein and 7% fat.
The pond is poorly filtered. The water turnover rate is once every 5-6 hours. There is one drain. It used to be a retrofit bottom drain which never worked and was finally changed to a crude skimmer to catch the leaves. It’s under a large tree and there is a LOT of leaves. Every month or so, I will net out the accumulation of sticks and decaying leaves. This stuff can get pretty thick, but is not generally anaerobic because the fish pick through it on a regular basis and keep it stirred. There is a lot of suspended fines. The ammonia, nitrite and nitrate are below detection on my Hach kits. Oxygen is not saturated, but is high enough to make me comfortable. Water exchange is about 150% per week.
There are also thousands of christmas red guppies in the pond and a red-ear slider (turtle) female crawls over from the adjacent mud pond every afternoon at feeding time. The turtle eats a little of the feed. The guppies pick at it until the koi are ready to eat, but they do not make a dent. I am pretty sure the tosai eat a few guppy fry. There is some water hyacinth in the pond, but it’s too shady to grow well and the koi keep the roots pruned back to little nubs. When I scoop the debris off of the bottom, many amphipods, midge larvae, leeches (a small non-parasitic species) and other creepy-crawly things can be found.
As horrible as the system sounds, I am very pleased with the condition of the fish. There has not been any sign of disease since the fish were placed in this pond over a year ago. The growth is really good. I put my best tosai here because they grow much faster in this pond than they do in the tosai pond. A couple of the koi have an "imposing" physique. All have a torpedo shape and none have a pot belly. The backs (where fish lose weight first) are full and rounded.
My only explanation for being able to get away with such a low feed rate (when expressed as percent body weight) is that (1) the fish density is reasonable, and (2) the wastes are recycled several times and the nutrients keep coming around again as natural koi forage.
I will mention that, for food fish, 1-2% body weight per day is considered a high feed rate used only for young, rapidly growing fish. Very small fingerlings may be given up to 15% per day. A maintenance ration for mature fish is generally about 0.5% per day.
-steve hopkins | 
06-04-2005
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