YOu can make very small batches of food - it is not necessary to make 2 gallons of the food - nor is it necessary it incorporate ALL the various food substances in one food.
I generally think about 1 package of gel per 1 cup of ingredients. You need some liquid - I generally use as little as possible to liquify the veggies - and let the liquid that is in the gel when you dissolve it be the general liquid.
Blanch all veggies - cooking them for a few moments in boiling water. I tend to do them in the microwave with as little water as possible. Steaming them also works. This will break down the enzymes in the food so it does not spoil when it is frozen.
You can throw just about anything you want into the mix. I have a batch that I keep at all times - just peas and spinach. (A few months ago it became all peas, when my spinach in my garden was done and you could not buy fresh spinach on the market!). The fish love it.
If I have sample packets of fish food given to me, I toss those in. Vitamins, fruit, etc. are all good candidates..... I like to keep the fruit and the veggies separate to a degree. My fish seem to eat them better that way. You can soak and reconstitute dried krill, etc. to add extra protien to the food. It is good stuff.
I have a whole section in my freezer that is nothing but fish food - right next to the cat food. My hubby knows not to try any of it. When the kids visit - we have to be careful. My new son-in-law did not know - and was feeling adventuresome. He tried some krill/tuna mix. He did not like it.