You might be able to get them to sink if you soak them for a while before adding them to the tank. You can also try hand-feeding him, or using a turkey baster to get the food directly to him. Wet-frozen foods are a better choice, as some sources say that the freeze-dried type tend to cause bloat. It sometimes takes them a day or two to settle in, moving to a new home is very stressful.
However, I do NOT recommend that you keep this little guy in a tiny bowl without filtration or heat. If you can't afford to get him a proper tank (at least 2.5 gallons, filtered and heated) you really should return him to the store. They also jump - so keep that in mind, also.
Sorry to be harsh. . .
Last edited by Chesh; 07-23-2012 at 04:39 PM.