SO far there some interesting info on VHO:
<span style="font-family: Arial,Verdana,Sans-serif;">
<span style="color: #ffff00;">
alt="" /> VHO Fluorescent</span>
<span style="font-size: 12px;">
VHO is short for "very high output." These bulbs operate in the same way as regular fluorescent bulbs, except that the ballasts that power these lamps apply more electrical current to the lamp, and some brands of VHO lamps employ more phosphors in their operation. Typically, a VHO bulb produces twice the output in lumens as a regular fluorescent bulb. They also tend to burn twice as hot as regular fluorescents, although some new VHO electronic ballasts allow the lamp to operate at cooler temperatures. <span style="font-family: Arial,Verdana,Sans-serif;"><span style="color: #ffffff;">It has been our experience that VHO lamps seem to degrade faster than normal fluorescents in terms of a ratio of output in lux over time when measured underwater with a light meter.</span></span></span></span>
<span style="font-family: Arial,Verdana,Sans-serif;"><span style="font-family: Arial,Verdana,Sans-serif;"><span style="color: #ffff00;">
What we mean by this is that we have measured</span> a faster reduction in intensity over time for VHO lamps compared to when the lamp was new than what we've measured for normal fluorescent lamps. </span><span style="font-size: 12px;">We base our opinions on our observations. What we have observed is that in VHO-lit reef aquariums, some hard corals begin to close slightly and algae growth is retarded after about four months. We change the bulbs, and the animals and algae spring back to life! That simply doesn't happen as often in the reef aquariums we maintain which use metal halide and/or Power Compact lamps. Therefore, for reef aquariums that employ VHO lamps,
we recommend changing these bulbs two to three times a year in order to maintain the overall health of the environment. </span></span> <span style="font-size: 12px;"><span style="font-family: Arial,Verdana,Sans-serif;"><span style="color: #ffff00;">
The other problem we have encountered with VHO lighting</span> is that for some reason (we don't know why), VHO lighting ballasts seem to fail more often than any other lighting ballast we've used, and we've used hundreds! This seems to be especially true of the newer, electronic ballasts that are being sold these days. We consider VHO lighting systems to be expensive in terms of bulb-replacement, and in our experience, subject to ballast failure. We do know that IceCap®, a major manufacturer of VHO ballasts, has made great strides in developing electronic ballast technology that promises to considerably extend bulb life, so we haven't given up completely on VHO. VHO still holds one advantage over their competitor, Power Compact lamps, in that the lamps distribute light better over a greater area.</span> </span>
