Lance's 225 gal tank

[Lance]

Well I came down at 3am to check things out and couldn't see anything. The water level in the tank is fine and no wet spots anywhere. Checked again at 6am before going to work and again just now: no apparent problem. I think it must be the reflectors cooling down. The sound seemed to come from up higher. Don't know why this would happen all of a sudden, the light has been on the tank since May?