"Gorf" wrote in message
oups.com...
Hi, folks.

I'm posting this on behalf of a close neighbour, who's noticed a
behaviour change in his Koi. I know a little about tropical aquaria,
but nothing about ponds and Koi, so wysiwyg (if you need extra info,
you'll need to ask: I'm going to write all Iknow about the problem).

The pond is 3' deep with a right-angle triangle top-down profile - the
hypotenuse (long side) is 3'. It contains four Koi of varying sizes,
and four large goldfish (although they are only slightly bigger than
the smallest koi). It has an infra-red and biological filter. There is
no aeration from bubbles, that is done by the agitation of the surface
at the filter return.

The behaviour change is that the koi (only) have suddenly started
resting on a ledge at the surface, whereas before they would be
swimming at the bottom. The goldfish are still swimming about the
bottom. Their response to human approach is lethargic - and one was
seen today hanging nose down at the surface.

There are no obvious marks or cysts, all the scales are flat, eyes
clear. They don't seem to be gasping.

They haven't been feeding for a few weeks - the owner is worried that
they might not have built up a reserve to let them overwinter. He needs
to stop feeding them very soon. For this reason a quick response would
be appreciated

The only noticeable change is some lichen-like blooms on the inside
surface of the pond.

Sorry if this isn't enough info for a full diagnosis. I'm going to copy
this to the owner and he'll add anything that might be relevant or
correct anything I've got wrong. In the meantime if anyone takes a
potshot at answering this and needs us to go look for something
specific, let me know. He's just up the road and even if I can't get a
response, I can get in his garden and look for myself.

Thanks for looking...

G

Sounds like a water quality problem. Has you
neighbor tested the water? That's a very small
pond for that many large fish.

Think about your tropical fish tanks, the same
principles apply. Overstocking = major problem.

Can't hurt to suggest a partial water change -
see if that helps. Then suggest he do something
about the overstocking. Either give away some
fish or build a bigger pond, fast!

The usual recommendation is 1,000 gallons for
the first koi; 200 gallons thereafter.

Gail