Replaced all bulbs in February. All ATI t5ho. Aquablue special 12k~Coral plus (Max Par) and 2x blue plus. It's 11 measured inches from the lights. Lights run for 8-10hrs a day. The DIY holder is made out of EPO-Putty. I did read though that their mantels will fully open in order to acquire more light, so now I'm feeling bad. I'll work on removing the holder. Not sure where I'll put the clam though