As long as he is active and looks healthy he can go quite a while without food. He's so used to the fish that he doesn't recognize worms or pellets as food yet. He can fast for at least a couple of weeks before the situation becomes worrisome. Just keep offering reptomin and worms every other day or so. Most likely he will eventually get hungry enough to try some. You might have given up to easily on handfeeding the earth worm. Try again and keep following him around the tank with it. You can give up after 5 min or so, but let him get used to the smell. I don't recommend using forceps to hand feed. If he gets really excited and tries to lunge at them he could poke an eye out or worse.
So don't worry, you're doing everything right. The tank looks nice. Keep up the good work! and buy a filter![]()