Feeding him mice is fine - however the bigger he grows the more mice you will have to feed him. It would be easier to feed him one rat per feeding as opposed to 6 mice which is what he's likely take once he reaches adulthood.
First try switching him to rats - buy him a little one wean size - they can't do any real damage. If he takes it without problems, the following week get a slightly bigger one - and work your way up to appropriate size.
Once you've got him established on rats you can start feeding him live off of hemostats - once he gets used to taking the food from the hemostats you can try fresh killed from hemostats and then onto f/t (make sur eyou warm it to about 98*.
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Tosha 
"Nihil facimus sed id bene facimus"

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