Bubblers are not common in salt water aquariums mostly because of the salt creep and extra evaporation they create. Exceptions being quarantine or hospital tanks using air pump driven sponge filters and emergency situations when extra oxidation is needed. But if you don't mind the salt creep and evaporation then there's no harm in better oxidation. For most tanks it's the overflow, powerheads and skimmer that provide enough.
I would stay way from stone other than reef tank specific dry or live rock. Never know what kinds of metals or other contaminants could be in them. There is no reason to think that a plastic aquarium decoration would cause red slime.
