changing filter


I am wondering a few thing. I just recently purchased an adhi45 refugium. I have been running a wed dry filter for the last 3 years on my 110 gal reef tank. Will I be able to switch right over to the refugium or will this mess any of my biological cycle up. Please let me know what you think. Also I want a mag drive 18 for my return is it possible to go to big for a return pump. will there be too much flow going in and comming out.