There seems to be a lot of conflicting stories about the 3 types of actinics. Many swearing that the VHO's can't be touched, and others saying that T5's are the most efficient. From my perspective, simply on cost the VHO's are cheaper because there are 2 bulbs instead of 4. The individual bulbs all seem to cost the same, so my annual bulb cost is 1/2. The electric cost of 2 VHOs or 4 PCs or T5's is almost exactly the same. The only remaining variable, is which gives better looking (and feelnig for the corals) light..