We inherited a pond when we bought our house 2 years ago. There were
already 4 goldfish in it but we added two koi, one of which we never
saw after a few weeks.

Good combinaation Gold fish and Koi so the chances of offsprings being
mutts are great.Mutts or lullets are mixed and not worth a dam in
regards to anything but eating food and making a mess. Ask carol
gulley about half breeds, she is an expert in that area. from what I
hear.

Today, my gf was cleaning a bit of weed out when she netted a small,
green fish that had a silvery gold underside. One of the existing
goldfish had been looking a bit chubby recently(!) so is it possible
that it has spawned?

So, a few questions....
Are young goldfish green?

Yep, as well as black, green, blue, red, orange striped, polka dotted.


Is it likely that only one would have survived or should we expect
more? (i.e. how many fish are expected from 'a spawn')

1,355,290 on average



Is there anything in particular we need to do to assist it?

Yep, they sell fish formula at lfs and smallnursing bottles. They need
to be fed every 3 hours and burped. Diapers are optional.

When should we expect it to change colour? Xeno

Ask the fish, its his / her decision. It may be blue todayb and black
tomorrow and green the next......they are like that.


-----------------

My opinion and only my oipinion. Opinion its the whole thing!