If I pick up some frozen food, that is most likely going to defrost before I get home, then re-freeze it, before feeding to my fish (will thaw before feeding any to them), will that cause me any problems?
That was my thinking, not that I think it will make much difference but I am talking about frozen bloodworms, and they will likely be out of a freezer for about 3 hours or so.
Use a cooler! If they are going to be unfrozen for that long, and they begin to get "mushy" then they are no good!
I made this mistake a few times, you should never refreeze thawed out frozen food.
Luckily I had fish who would just refuse to eat it... flat out. Then I knew something was wrong.
Don't risk it. I tried using bloodworms once that I didn't think had spoiled (but they had), and they fouled my tank to the point that I thought I was going to lose all my fish. Although I did a major water change (e.g. 50%) about 3 hours after the fact and installed a new bio-wheel filter to supplement my other filter, I still lost about half my fish. From my experience, it isn't worth the risk.
What I do is take what is about a 6-quart cooler, put about 2 quarts of water in it,
add about a half-cup of salt, then fill it about half-way with ice.
I then take this with me when I go to buy more frozen fish food.
This keeps the food frozen for the about an hour the return trip takes.
I would defiantly use a tiny cooler maybe just a thermos with crushed ice inside and just brake up the package with a small hammer so it will role inside the thermos opening. The cubed blood worms bend pretty good.
If its allot of frozen food I would just use a cooler with dry ice.
Three hours is a long time in the heat we have been having I wouldnt risk it. Now if you are talking about picking them up when you leave the city and driving STRAIGHT home then I would say yes, but 3 hours no.
frozen fish food is fine if it is thawed out, as long as it is as cold to the touch as a can of soda or beer is after being in the fridge overnight. then it is fine to refreeze because it hasn't spoiled. if it is barely cold to the touch or warm toss it, but since your going three hours get the cooler like everyone has suggested.