Comets harassing large fan tail

[sussexpond2017]

Hi all,

This is more of a goldfish question than a koi question - I hope that's ok. We recently completed our pond a few months ago and in August added 2 koi and 4 goldfish (3 smallish comets and 1 large fantail). We have noticed the comets and fantail tend to stay close together but over the past day saw two of the comets completely harassing the large fantail, chasing it around the pond and nudging aggressively at its flanks. I tried to bat them away but they would not be deterred. The fantail is getting pushed into very shallow water on top of the marginal plants and I'm afraid it will jump out of the pond or get stuck. Is this mating behavior? Should we separate the fantail? The koi and the remaining comet leave the fantail alone.

Everyone seems to be healthy, I have seen no damage on any of the fish.

Any advice appreciated! Thanks.

[RichToyBox]

Sounds like spawning activity. It should be over by now. The act requires some rather harsh pushing of the fish, usually against the side of the pond or pool to push the eggs out of the female, which are then fertilized by the male's milt. With koi, it is the same, but the level of organics involved will trash the water quality, increasing the ammonia and subsequently the nitrites to the danger zone, so you might want to keep an eye on these. With koi, often there will be a definite aroma, from the spawn, I am not sure there is enough with goldfish for you to notice or not.

[sussexpond2017]

RichToyBox, you were exactly right. After a few hours, the comets left the fantail alone and the pushing stopped. I didn't smell anything, and the levels are ok. Thanks so much for the information and quick response.

[nmtsaki]

Any eggs or babies yet??? they end to have millions. Time to get them spayed or neutered. Obviously, not possible, but you may want to separate them out, since you know what sexes they are, or just scoop out the eggs. Goldfish can overrun a pond rather quickly, and 6 can turn into 100's. Koi can breed with goldfish also, but the offspring are supposed to be sterile.