Frozen and freeze-dried living foods

Frozen and freeze-dried foods retain all the vitamins and protein of live food, as long as they're stored absolutely dry or kept firmly frozen. When freeze-dried food isn't kept perfectly dry, the slightest dampness begins bacterial fermentation, which degrades the nutrition. Freeze-dried food goes stale this way. I keep a dessicator canister saved from a medical prescription in each opened can. Don't leave the lid off. Freeze-dried brine shrimp, daphnia and bloodworms have become standard fare.
 
The one element forever lacking is the appeal of the living creature itself; its movements elicit feeding responses in fry and fish. Not all fish can be weaned off the living organism, "wriggling", as Gollum says.
 
Keeping frozen food frozen is essential to maintaining its nutrient value. It's worth taking two frozen cold-packs from your freezer and rubber-banding them together before you go shopping for frozen food: the packets of frozen blocks can be sandwiched between the cold-packs for the trip home to your freezer.
 
Since bacteria are routinely archived in the freeze-dried state and kept in labs for long periods, after which a percentage of the population revives and multiplies when water and nutrients are restored, then it's reasonable to ask whether freeze-dried living foods can introduce bacteria. Yes they can, is the answer, but only the normal, non-pathogenic strains of bacteria that are already everywhere in the aquarium.
 
Currently the freeze-dried living food menu in my cupboard is: Freeze-dried Bloodworms. Hikari Freeze-dried Daphnia. In my freezer arecubes of  frozen daphnia and frozen bloodworms. I keep them in a closed zipper-locked freezer bag, partly to reassure my household.
 
About vacation blocks. Those "vacation blocks" were devised in the 1950s, surely by front-office suits in a marketing department, I've always imagined, and not by aquarists, who soon learn that mature fish thrive on a regime that includes some "starve-days." Even the simplistic aquarium sites geared to children warn that "vacation blocks" aren't a substitute for regular flake feeds. These blocks with flecks of embedded feed are molded of gypsum (plaster-of-Paris), which is calcium sulfate (CaSO4). Calcium sulfate does not contribute to the alkalinity (carbonate buffering), but it does contribute to the general or permanent hardness, the "total dissolved solids." Not a desirable effect.