Being unfrozen for a bit while the bag is sealed shouldn't cause rotting. Did you make sure to fully thaw the food before feeding? cold food is not great for fish.
Since I only have a 30 gal. I just put the cube in the tank, throw a rubber glove on, shake the food, and the fish go nuts. I then pull out the remainder of the food put it in a container and refreeze...
ah, that can cause some issues. Remove a cup or so of tank water and put the cube inside of it to thaw when feeding in the future.
Since I only have a few fish, I can't use the whole cube. Is there a safe way to use a bit of food and then refreeze?
its not the worst, not great either.
remove a small portion of the food. If its in pre portioned cubes, cut the cube into a good portion, then defrost in a cup of tank water
That way the bigger portion of food will stay frozen, and I can put it back in the freezer correct?
Yep. This is what I've always done, and especially so in my 13.5 gallon tank. The food is out of the freezer for maybe 1 minute total. The small chunk of a cube (about 1/3 for me) goes in a shot glass with tank water to thaw, but the package is immediately back in the freezer.
