It will be big enough if your just moving everything over to the 72 gallon. I (assuming this is a cycled tank) wouldn't mess with the cartridges or pads in your Magnum pump(but keep 'em wet when your moving everything over), or you'll be starting all over with cycling the tank.
What else can produce nitrate? wasn't expecting it at day 5 of my cycle.
Nitrate 80 ppm
Nitrite nil
Ammonia 1 ppm.
I will mention that I added nutrafin cycle. 5 fish (mollys) in 20 gallon tank