Marine mix is commonly used here.
Add some raw fish (white bait, etc), raw prawn/ shrimp, mussels (without the shell), squid or octopus and some spinach to a meat mincer.
Run it through the mincer a couple of times and then mix the stuff up in a bowl. Put some of the mixture into a plastic freezer bag and flatten it out so it is thin (no more than a couple of mm thick). Then freeze it. You can use ice cube trays instead and simply add the mixture to the trays. Freeze and then put the frozen blocks into a bag or container and keep frozen until needed.
You can add other meats too if you like but try to stay with marine/ fish based meats.
You can also use spinach or any other vegetable, or you can make the mix up without any veges. Some people make up a vegetable mix for their herbivorous fishes.
Depending on how big your fish are will determine how many times you put the mixture through the mincer. For small fishes like tetras you might need to mince it 3 or 4 times. For bigger fishes like medium sized South American cichlids, it might only have to be done once or twice.
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I collect aphids from the roses when they are available. I also swat flies and mozzies and feed them to the fish.
You can culture daphnia in containers outside under a tree. You often get mozzie larvae in the same cultures.
