Switching back to T5 from LED

[Myka]

I highly doubt it's the light switch causing your problems. How high off the water was the Kessil and how high off the water is the ATI? Assuming typical light heights, I would think your corals are probably getting less light now with the T5 turned down so low. I assume your new tank is bigger than the nano? You added rock? Dry rock or live rock? Did you cycle it first?

That said, in my SPS tank (36x21x21") I can't turn my 6-bulb ATI on at 100% using all ATI bulbs. I have CH1 on for 12 hours a day at 100%, and CH2 I can't go beyond 70% for 6 hours. Maybe you want to disconnect one of the ballasts controlling 2 bulbs or look for a trade for a 6-bulb or possibly just use lower PAR bulbs. Sounds like an awful lot of light for a mixed reef. I don't think that's your problem right now though.