Food is food to a fish. And most of the algae-based sinking foods do have fish/meat in them too as fish need all of this.
In your situation, dropping in the wafers a couple hours after the tank is in darkness might work. The Betta will not be active in the darkness (darkness meaning total complete blackness, no ambient room light). Snails will certainly be active during darkness, not sure about shrimp so the shrimp experts can advise on them.