Well, I don't want to assume that the pond will be finished on schedule. Projects never go as scheduled, so I'm not comfortable putting too much strain on the 40 gal with fish that could easily outgrow it if they are in it too long. That's why I was thinking rosy reds or maybe white clouds. Something that will not get big, but can still keep this guy company in a cold water setup, and something that can live in the pond once it is set up and running. Ideally that will be late next spring, but again, I don't want to assume that all will go as planned.