how big does a Jack Dempsy be before I start feeding it live food, such as earthworms and gold fish..please help i am new to JD's.
More than 10 years
Welcome to Fishlore Nicky.
Best not to feed Goldfish to your JD. There are better feeder fish around & feeders are not essential to a JD's diet. Gold Barbs are the most common feeder fish to buy here in Aus but you would be best served by breeding your own Guppies if you really want to provide live fish for your JD so that you can avoid many of the diseases often carried by feeder fish.
You can feed live Brineshrimp & Bloodworms once the fish is about 1" long. Earthworms can be chopped into small pieces suitable for feeding to your fish once they have been properly cleaned.
Jack Dempseys can live very happily on a combination of the commercially available flakes & pellets. You can also buy frozen Bloodworms, Brineshrimp & mixed foods that are good for weekly treats.
I would stay away from feeder gold fish. It would be easier to just feed it a staple diet of flakes/pellets but if you insist on feeders, you should breed your own to avoid the spread of disease. If its at an inch long(tip to the end of the tail fin) you could cut up the earth worms so they fit in your fish's mouth