Filter is just an overflow sort of thing. It pours into the back compartment and flows through whatever media you have before it is pumped out by the pump it comes with. And it needs a ph because the output from just the return pump isn't enough to keep the water moving in the entire tank.
It doesn't come with a heater from retailers, you should see if he is including it. And GFO
is granular ferric oxide, removes phosphates, keeps algae in check.
Oh Kelsey, the 24 doesn't come with powerheads, just the return pump. And I suppose you can put the heater in the back, but I have mine packed with media lol.