Hmm...

I think the water temperature question was right on.

I'm in San Francisco and the temperature here is typically pretty mild and stable, so I guess I figured that with a "cold water" fish like carp, ambient temps would be fine. Clearly I was wrong! I got a thermometer yesterday.

We had a reasonably hot day for us, and at 4pm (about as hot as things would get I figure) the water temp was 64F. We had a not very cold night last night and this morning the water temp was 58F.

From my reading it seems that Koi typically like for things to stay above 59F and that water in the 70s is really ideal... so I've definitely been running cold. I was hoping not to have to heat my tank, but it looks like I'll have to bite the bullet.

I should be able to get the temp up and more stable pretty easily with a small heater. And I'll post results in a week or so.

Thanks.

Bill