I just spoke with Barry of Clams Direct and asked him about HO T-5 lighting and keeping clams. He stated that many of his customers use HO T-5 lights and keep clams without problems. I specifically asked him about T.Crocea clams the most light demanding and he stated that they should be ok as long as they are not on the bottom of the tank. Now I only asked him about my T-5 set up which is 8x54watt bulbs. He also recomended using 10k bulbs. I hope this helps people considering HO T-5 fixtures. In my book MH's are the way to go, but I have heat issues with my reef tank because its in a loft.