For some reason fish that ignore most prepared foods will still tuck into paste food. Many killifish just won't entertain flake foods, or even if they do are very fussy, and hardly get excited when fed it. Although killi keepers generally culture live foods for their fish, there are times when there is insufficient food available, or no time to collect it. Paste foods are highly nutritious and seem to be enjoyed by the vast majority of killies, even very fussy species.
The recipe I use is adapted from several others with my own additions - generally because those were the ingredients I had. The ingredients are listed below, with approximate (I never weigh anything when make this) proportions by weight. Put the whole lot into a blender until its just a liquid. If you use heart you should blend it separately with a small amount of water; otherwise you can burn out the blenders motor. Add or skip anything- save a little here or there from your own meals (especially if you’re shelling prawns) and stick them in the freezer. I would imagine this food tastes similar to most crustaceans that our fish would eat.
I also add a few other things for various reasons, and when I remember. The amounts are based on making a whole blender full.
Once its all mixed together you can add more water if it's too dry. Ideally the mix should be a paste. Once you’re happy with the ingredients boil up a cup of water and dissolve 2 sachets of gelatine. Make sure the water boils and all the gelatine dissolves. Blend this into the mix as well. You can spoon the mix into zip-lock bags, lay them flat and leave to cool overnight, preferably in a refrigerator. They will gradually set. The next day freeze them. Defrost what you need, as you need it.
The only time my fish ignore this food is if it gets caught in the hornwort and they don’t see it! Paste food does sink, so is less useful for surface feeders than other killifish, but surface feeders certainly do eat it. It will generally be eaten as it sinks, but nothos, for example will pick at it on the tank floor. Being a finely blended paste, the food can be 'broken' up into as small pieces as needed. Try not too put too big pieces into the tank, and not to overfeed. Paste food is obviously very rich, and uneaten food should not be left to decay in a tank. If you keep apple snails with your killifish, they will clean up for you, but otherwise you will need to syphon up uneaten food.