Aquaclear 70 pushes about 400 gallons per hour at 0 foot of head... I'm sorry to say man, but you are grossly underdoing it right now! lol.
Here's what I would do... I would add the aquaclear 70 to the display tank for extra water flow. Then, I would put a minimum of a mag 18 on the tank. The aquarium needs at least 10x the amount of flow through it. ... if you are concerned if the mag drive pushes too hard, just add a ball valve.
good luck!