Be careful when defending against Stun Gas Bloon, as all monkeys that attack it will be stunned for 1 turn, guaranteeing that it cannot attack or reload at all on the next turn.
The Stun Gas Bloon can exploit Monkeys with multiple ammo, especially those who are defenders or attack multiple targets.
Mortars have no control over hitting a target, so Stun Gas Bloon is a good counter to them, especially The Big One.
Heroes cannot be stunned by damaging it. Quincy is by far the more reliable choice for popping Stun Gas Bloons, alongside Adora with her passive activated.
Powers are unaffected by Stun Gas Bloon. Super Monkey Storm guarantees that Stun Gas Bloons are removed. If there's a few bloons on board, Storm Of Arrows can work.