Undergravel filters

[AcTwisted]

was looking to get one for my 150 gallon tank. it would need to be 72"x18".

Perfecto sells one...... are they reliable units?

also as far as Powerheads go, what flow rate do I need & how many would I need? I see the AquaClear 402 is 250 gph.

please help someone who's never used powerheads & undergravel systems.