Nightcrawlers are made up of mostly water, but so is fish. There is more than one subspecies of garter snakes that are earthworm specialists and will feed just about exclusively on earthworms. I do not agree with the rumors that night crawlers are void of nutrition. Worms choose nutrient rich soils and decaying plant matter as their food. Meaning they are packing lots of nutrients into themselves even while swallowing soil. I would still supplement with vitamins and calcium on occasion, but every feeding would be overkill. I can get silversides at the grocery store by me, but most don't carry them.