If you mean tank size for the CAE, it needs a bare minimum of 30 gallons and must be kept alone. As it matures, it will attack everything and anything around it.
Edit: Just spoke to a friend who owns a CAE--and regrets ever buying it, but can't find anyone who will rehome it. She says 55 gallon is the minimum tank size for that one fish because of how randomly it can become aggressive and suddenly kill everything around it.