To make paste foods you need a blender and some sealable plastic sandwich bags. The ingredients are up to you. I start with a small can of tuna or salmon. Make sure it is water packed, not oil packed. Put it in the blender. From there you can start customizing for the type of fish you are raising.
I like to add shrimp, squid, crab or other sea foods. Occasionally you will find small bags of these sea critters on sale in the frozen food section of the grocery store. If you just want shrimp, the small salad shrimp are your best buy. I have also used beef heart, but that is rarely available where I shop.
If you are raising aquarium fish like Jordenella floridae, live bearers, or some types of cichlids that require vegetable matter, you can add that. Some suggestions are peas, spinach, and zucchini.
Some people add things like a vitamin pill or cod liver oil to improve the food value of the paste food. I have not tried this, but will some day. One thing I often add is garlic. It has been said that intestinal parasites can’t handle the garlic.
I once had a pair of a rare strain of Aphyosemion elberti. Before I could get any eggs the female started wasting away. I tried some parasite medication but it didn’t seem to work. I then made up a batch of paste food with an extra dose of garlic. The female started recovering and I was able to get a few eggs. I can’t prove the garlic was the reason, but it seems reasonable.
Blend the mixture until it is a puree about the thickness of a milk shake. You might need to add some water to get it going, but try to add as little water as possible.
The next step is the key. If you were to just freeze the paste at this point, it would just fall apart and cloud the water. You can get it to hold together with a little unflavored gelatin. Mix a packet of gelatin in as little hot water as you can to get it to dissolve in. Pour it into the blender and let it mix into the concoction for a few seconds.
Now you need to move fast! Pour the mixture into sandwich bags. You want to put in just enough to so that when you let the air out and seal the bag you have a square about ¼” to 3/8” thick. Lay the bags flat in the refrigerator for a couple of hours until it firms up. After that you can store it the freezer.
When you want to feed your aquarium fish, break off a chunk and chop it into the desired size with a razor blade or sharp knife. You can also use a grater to get fine pieces.
If might take a feeding or two until the fish get used to paste food. Once they do, they will really go for it. Even picky eaters seem to like it. I once had some wild darters. They would only eat live foods. They would not even accept frozen brine shrimp. They started eating the paste foods the first time I tried them.
Paste foods are a great way to supply high quality tropical fish food at a reasonable cost.