I make a conconction that my fish love. I adapted it from a DIY article out there to make this hard frozen veggie bricks.
I boil a pound of frozen peas, then a blend them in a food processor while stirring in 1 package of plain gelatin mix. I throw in a couple of raw deveined, shelled shrimp as well. Keep blending, then I add in a teaspoon of minced garlic, keep blending.
Once its all very uniform, I pour a small amount into a zip lock sandwich bag. The I force all of the air out of the bag, zip it and flatten the mix. I stack the pile of flattened bags in the freezer over night.
Then I take one out a crack into 3/4'' by 3/4" flat chunks. I throw one chunk a day into my tank and it gets devoured.
I will try and find the original DIY link I got the idea from.