I was all ready to jump on the band wagon here until I looked into my tank. I am not new-commer to keeping these animals, I've had many over the years. Today, I have 3 in my 120. Two are directly under my 250w metal halide, about 10" down. Both of these have bubbles on the upper tentacles, the lower ones no bubbles. The third is off to the side and displays no bubbles. This has got me thinking??? I never really knew why some do and some don't. He could be onto something here. I am not completely convinced but it certainly is an interesting theory.