Filtration and heat depend on the type/size/quantity of fish, where the tank is located, and the amount of light over it.
My 125 has 2 AC110's, 2 Rena XP2's, a Fluval 304, and 225g rated wet/dry running 500GPH.
Six 36" flouro tubes running 2x overdriven.
One 200 watt stealth heater, and three...