Hi bro,
I am on a 48X18X18 with IOS system as well. I had converted one of the chambers to a refugium with 24X7 hours lighting with caulerpa algae. Before I did the refugium, my tank was hoovering about 20 ppm for nitrate. Now, my nitrate levels are almost Zero!
IMO, having a refugium is very effective, at least for my case.
As for changing water, I am the lazy type and since Nov last year, I only did one 10% water change. I am very sure many here will disagree with me on my way of water changing. Somehow, my tank and my LS is still ok. Having said that, I will be doing some water change about 10% this week end.