Way too small to starve 3 weeks.
OP, you have to convert it, not starve it. A transition if you will.
Take your frozen feeders. Toss some in a blender and add tank water or purified water and blend. Make it very liquidy, and have your pellet of choice (id go with NLS) and soak the pellets over night. Make sure not to use too much fish liquid maybe fill to where the pellet is 1/4 submerged. Leave it in an open container. Itll soak all the way through and dry out a bit. Make sure its not super mushy or else when they chew it, itll make a huge mess. Make sure its soft but not mushy.
Eventually add less wish to water ratio until its only water. Then transition from soften pellet to harder by less water or drying out longer until its on pure pellet.
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