Thank you for your interest in Drs. Foster and Smith. VHO Lighting or Very High Output Lighting is specialty fluorescent lighting. VHO fluorescent bulbs are similar in design to standard fluorescent bulbs, but use a special fixture and ballast to produce up to three times more light than a standard fluorescent bulb. You will need a ballast that is high output in order to handle the watts of the light. If you aren’t sure on your particular unit we suggest contacting the manufacturer as using an incompatible light is a safety issue.
If you are looking for a brighter light to use without changing the ballast we suggest reading the article below as it should help you determine which lights might be best for your particular aquarium.
Aquarium Lighting Selection Guidehttp://www.drsfostersmith.com/pic/a...