I saw three AIs on a 180 today and they lit the tank very well. If you have full out sps I would probably get a few more, but for a mixed reef tank, three is plenty IMO.
Just want to point out that AI does not have a 2x2 coverage I called and talked to aqua illuminations and they recommend one unit for every square ft. So for my tank I would need 6 AI units @ 400 each so 2400 plus the controller. Radion is rated to cover a 2x2 area @ 750 each so I would need three which brought my price to 2250 no extra controllers needed. I actually saved money and got piece of mind going with radion and I dont regret it at all. That being said if my tank was deeper I would have prob went with AI my good friend runs AI over his 300g sps reef and he has amazing results. My opinion shallow tanks go with radion and youll save money, deep tanks go with AI to get penetration rather than coverage. Comparing the two is hard they have different mounting heights recomended and different spread I think they are for two different setups and neither one is a one size fits all. Even with the new TIR lenses I would be hesitant to put radions on a deep tank and I am an owner and a fan of radions. I think deep tanks would just be better off with AI.
