+1 although i'm in the lucky situation that i have large tank and 1 cube = 1 feeding. Always wondered what people do who want less as i always think the cubes are quite a lot of food even for big tanks.
Not something I would ever do either to be honest. I usually break a block with a knife now and put the rest back in the freezer.
It is frustrating but I never seemed to use a whole blocks worth even though I have 4 tanks running so I stopped defrosting a whole block, half of it used to get washed down the sink
i defrost 10 cubes at a time as i got loads of fish, i put them in a chinese takeaway dish and add tank water, leave for 30 minutes and spoon into tanks.