Bringing tank temp down by that much using fans (evaporative cooling) is going to present a new problem: humidity. For years, I used fans to cool my 125 with 3 400s from 84 to 79. The basement felt like Florida in August. It was so humid, it made it hard to sit and enjoy the tank. I recently redid my lighting and went from a hood to an open top using 3 lumenmax elites. There are no provisions for fans, so I was using 2 floor standing fans to cool the tank. The humidity got out of control. My dehumidifier would run all the time and really didn't seem to do a thing.
After talking to people with much larger tanks, it seemed that a chiller was the answer. From what I read, a 1/4HP would be plenty, so I bought a 1/3HP model just to be safe. Took me about an hour to plumb it into my return and the results have been amazing. The tank stays cool (79) and the humidity in the basement went from 65-70% to 40%. BIG difference. The basement is comfortable now, and I can sit and watch the tank without breaking a sweat.