These guys eat aiptasia that grows in your salt water fish tank.
They are reef safe,won't bother corals or fish and if they die do not release toxins
Their only food source is Aptasia, so once food source is gone, they will die.
At least 1 Berghia per 10 gallons is a good start. They hunt in packs, so 5 minimum.
Small- DO NOT BUY SMALL. THEY DO NOT LAY EGGS AND YOUR CHANCES OF SUCCESS WILL BECOME LESS.
Large 1/2"+ approx
Extra Large 3/4"+ approx