I had 4x110 vhos on icecap ballasts on my 90g. I had great growth, low heat, energy use etc. Just switched to ATi powermodule 6 bulb t5...lower energy, cooler, and brighter. I especially love the POP of the colors and bulb selection. VHO's are great, and more efficient than MH for many applications, but for a 55 a 4 or even 6 bulb t5 would be excellent.