my gold fish/koi

Question
ok.. i got a home tank with some 6 adult goldfish..and 1 koi fish...all my fish
have been swimming really close together and swimming very close to the
bottom..but my koi is rubbing his belly over the top of our biggest goldfish
and rubbing his/her side up against the gold fish..he/she also swims slowly
under my gold fish...but yet all the fish are swimming close together and
close to the bottom..and its a fairly large tank..are they breeding?...its also
pretty cold..i don't know if that might help...but i never seen them act like
that and was just wondering why..well i hope you can help!..bye

Answer
Hi April,
It sounds like your fish have the "shimmies". This can be caused by water fluctuations especially dropping to a low temperature. Goldfish do tend to breed in colder water which is normal. There is not much you can do about this as Goldfish can tolerate very low temperatures. This shouldn't be a problem.

Regards,
Chloe.