Well, maybe I'm overreacting. I just came back in from the pond, and one of the babies was swimming with the bigger ones for a short time before it went into the rocks again. Maybe they are just foraging. It just startled me how forcefully they were rooting into the rocks where the babies usually hide.

nancy1956,

Koi are herbies (herbivores), and they are hogs. They care only for where / when the next bit of food will be coming. Your little ones are safe from the bigger koi IMO.

LP

They might just be curious about the newbies. They only get rough when they are spawning. Then they can exaust the females. Sandy

Hello,

I've been raising koi with various degrees of success for about seven years now, though I still have little knowledge of the species, and I have never witnessed aggressive behavior of any kind, not even larger koi toward younger, smaller koi. Until last week, that is.

I had just thoroughly cleaned and restocked my little 90 gallon pond with youngsters, two regular koi and two butterfly koi. One of the butterflies was much smaller than the others, and they are only about five inches long. I noticed when I introduced them to the pond that the little one was not quite right, listing to the side when it came to eat, hiding alone behind the potted papyrus. It lived only a few days before it passed on, tho I had been doctoring the water with Pimafix and Melafix. The others are strong as tiny horses with appetites to match.

Back to aggressiveness: The one surviving butterfly is tri-colored, while the two regular are traditional orange and whites. The tri-color one evening began harassing the other two after I fed them, not attacking mind you, but running up along side them and pushing them, bullying them along almost as if directing them. It was very forceful behavior and went on for the whole evening. The little butterfly was still alive at the time, zipping aimlessly around on the surface, obviously in distress. I felt so helpless. But the tri-color did not approach it, only running up beside the other two and pushing them with its body.

So I googled a search on aggressive behavior in koi and found your forum, which I'm so glad exists. I was thinking that it might be mating behavior, though I would think they are far too young for that. I've had much larger koi, two and three years old (victims of a raiding raccoon that prompted me to build a fish coop.) The older ones never displayed any aggression, but then this is the first butterfly koi I've ever had.
Is anyone familiar with that particular type of koi?
Well, thank you for a chance to air my concerns. Sorry if I'm a bit wordy. I used to write novels for a living, long ago.

ldeanjames

Here is a link that might be useful: Window's Live Spaces

I don't know what the larger koi were doing when I saw them pushing forcefully into the nooks and crannies of the pond, but both babies have re-emerged and both look great. They're swimming around pretty close to the big ones, but mostly they're just staying together. I'm just glad they're okay. It bothers me when they go for weeks without seeing them.

We have a fish pond in our back yard with about a dozen goldfish and five koi. Recently we won a koi at a county fair. He was about 8" long, slightly smaller than our largest koi. A few days after introducing the new fish, he began following the big fish non stop around the pond. The fish would periodically nip or bite the face of the biggest koi, seemingly bothering the fish.

Does anyone have an idea what the behavior means or how to fix it?