Basic gel food:
Just like the foods our fish eat in nature, gel food is mostly water, and has a more 'natural' texture than pellets or flakes. Makes the fish feel 'fuller', avoids some of the potential problems of both hard, compressed sinking foods, and air filled floating foods.
Remember: if its safe for you to eat, its safe for your fish, at least in reasonable quantities. Tailor your ingredients so suit your fish: for herbivores, try peas, tomato paste, spinach, green beans, carrots, etc; for meat eaters, tuna, shrimp, salmon, FD bloodworms, etc. For omnivores [and most fish are, to some degree], use both veg and meat. Frozen vegitables are actually considered higher in nutritional value than fresh, canned is lower than fresh, according to the FDA.
If you are in a hurry, you could use pelleted fish food...
Vegitables should be lightly cooked to make them more digestible, canned meats can be used straight, but fresh or frozen meats should be cooked enough to eliminate the possibility of parasites or bacteria.
You want 2 to 2 and a half cups, ground fairly fine in a blender or food processor, with enough water to bring them to a 'milkshake' consistency.
Stir 2 to 3 envelopes of unflavored gelatin [available at any grocery] into a quarter cup of cold water, and microwave till the gelatin is disolved. The liquid will be amber colored but clear-- usually takes around 30 seconds.
For a floating food, add the gelatin mixture to the food in the blender or processor, and mix for a minute or two: that will incorperate enough air to keep the food on the surface.
For a slow sinking food, just stir the gelatin mixture into the other ingredients.
Line an oblong cake pan [9x13? whatever the 'standard' size is] with saran wrap, pour in your food mix, and refrigerate till set. This will give you a slab a little less than a quarter inch thick, great for medium to large fish. For smaller fish, use more than one pan, and shake the pan to distribute the food in an even layer.
Once set, cut the food into appropriate sized pieces. Try to cut it by pushing the knife blade straight down through the slab, leaving the slab as intact as possible. If the food is sticking to the knife, dip the blade in hot water.
Remove what you think your fish will eat in a week, and freeze the rest of the pan. This stuff tends to freezer burn easily, so once its frozen remove it from the pan and wrap it tightly. The frozen slab will break readily along the lines you've cut. Several days worth can be removed from the freezer at once, and thawed in the refrigerator.
The food must be kept frozen or refrigerated: it will re-liquify at room temps. Should last a week or two in the frige, 3 months in the freezer.
Using more gelatin results in a tougher food, but one that leaves fewer particles in the water. Less gelatin makes the food softer and messier, but allows even very small fish to nibble away.
I store the refrigerated portion in small ziploc bags: keeps it from drying out, lessens the chance your bloodworm potion will end up in the chocolate pudding.
Medicated Gel Food:
Anti-biotics delivered via the food not only saturate the fish's body in a way water bourne anti-biotics don't, they require much smaller amounts of medicine, and lessen the chances of damaging the bio-filter.
To do it right, you really need a kitchen scale that measures in metric. If it also allows you to deduct the weight of your container, so much the better.
Tetra's medicated food contains 10,000 mgs of tetracycline for each kilogram of food. Since a kilogram of food would be a BIG supply, maintian this ratio while decreasing the overall amount of product.
Since most tetracycline [should be available at any lfs or via the web at major retailers like drfostersmith.com] comes in 250 mg capsules, a convenient amount for most hobbiests is to mix 4 capsules [you have to open the capsule and pour out the powder] with a little water in a small container [the powder doesn't dissolve easily], and add the resulting 1,000 mgs of med to 100 grams of liquid food [if you have gel food on hand thats already set up, it can be re-liquified by placing it in a bowl over hot water. It should re-gel when refrigerated.] The meds need to be well mixed in, so as every bite has the same amount of medicine.
My best guess is that 100 grams will be roughly equal to half a cup, but I'd urge anyone with an interest in trying this to get hold of a kitchen scale. They aren't expensive, and available at kitchen supply stores, and stores like walmart.
I dye the medicated with a few drops of food coloring so I know at a glance what I'm feeding. I'm not certain the tetracycline remains effective if the medicated food is frozen.
All anti-biotic foods should be fed for a minimum of 10 days to lower the chance of an anti-biotic resistant strain of bacteria from appearing. I write the beginning date on the ziploc, just to keep things straight. To insure the fish get an adequate dose, its better not to offer other foods until the 10 days are up.
As with all new foods, it may take a couple of trys before your fish accept it eagerly. If you've chosen your ingredients well, they'll come to love it.