This Old Spouse
TOTM Winner May 2013
Why take any chances? Just defrost in a container of tank water and pour it in as Noahs Ark6 suggested. I would think you're taking the chance of injuring the fish in some way by putting a frozen substance in the water. Whether it's from cold pockets or from a fish pecking at a frozen cube, they aren't equipped for it, so don't do it.

I do defrost their frozen food though, it spreads out and gives them all a chance to have a bit
)
going to my local tropicalfish shop said back a couple of years now it was ok just to put the frozen food straight in to the tank even thoe I agree about melting it first in tank water as better spread or my yoyos wood woof the lot down. Do you not find that each shop all give out different information and gets really confusing.