The Puffer Forum

well yes / no ... frozen floats Thawed sinks.

It is best to thaw them and strain the dirty water ( a habit I neglect to do). That dirty water can create a film on the surface of the water. it is difficult to get rid of in FW set ups

Another reason to thaw:

Floating food means your puff will be eating at the surface. They may accidentally suck in air, and taking in the air with food can make it difficult to expel and may lead to death.