Yeah, you can raise them in tanks. But, the problem could turn into nutrient over load from their waste. You would have to change the water or partially change pretty often.
I have pondered the idea of setting a 100 gallon tote next to the pond, then run a small koi pond pump to pump water to the tank. Have an overflow gravity flow back to the pond. Could even do a bottom draw but make sure it didn't siphon.
If the fish ultimately will live in that pond they would already be conditioned to the pond water. With a reasonable flow through amount, shouldn't even need aeration. The pond water should already be aerated.
Clean bottom waste with water capable shop vac.
I have not done this. Just speculation.
