Years ago I did a lot of gelatin-bound DIY mixes like
FESHMAN
describes above. Mine were intended for use with larger predators and I cut the mass of food into individual cubes or strips that were used in place of feeder fish or earthworms., fed to fish that quickly gulped down the whole chunk. Ingredients varied, but were mainly chopped small bait minnows (caught myself and then frozen for a few weeks in an effort to kill off as many pathogens as possible, then thawed and chopped) and mayflies (which could be collected in season by the shovelful and frozen for use). I never included earthworms as these were simply fed individually as treats. I'm sure that store-bought fish or shrimp could be used, but I preferred the idea of using whole organisms rather than just "meat". Also, this was done as a money-saving endeavour, although I admit it was sort of enjoyable as well...smelly, messy, time-consuming, but fun.
I did smaller amounts of a similar mix for herbivores, mainly plecos and a Giant Gourami. Same animal protein, but with a large amount of duckweed making up the bulk of the stuff. I had a couple marine tanks producing armloads of Caulerpa, and I tried adding it but it was mostly water and I gave up using it in the mix, although fed it often as a treat as well. I'm sure that hair algae or other fast-growing plants like Hornwort, Anacharis or others would work. Green stuffs from the grocery store might be worth a try, but again, not as natural and not as cheap. This stuff was cut up into bite-size portions for the Gourami, or just big slabs dropped in for plecos and others to pick at.
Gelatin is very much a less-is-more thing; you want a mass of food that is just barely made cohesive by a small amount of gelatin binder, NOT a big glob of clear Jell-O with a few isolated chunks of food embedded into it. Takes trial and error, and once you find the right proportions of food and gelatin, it's easy and repeatable to make up that amount of mix over and over. Keep it frozen and break off as needed.
This is best done when your wife is out for the afternoon. Even then, you will likely want to get specific containers, tools and a food processor devoted strictly to this job.