When you say smaller I ohpe your not refering to the 10 gal
you posted the skilter question about. If so than you should know better since you say you have kept many groupers. Even a baby grouper is to big for a 10 gal
tank. Let alone adding another giant bodied fish to the tank. As im sure you already know they will outgrow the 10 gal
within a very short time. My guess will be in about 4 months depending on feeding.
MIN TANK SIZE 250
And given the potenal size of the snapper I would say an equivlent size tank for it.