The wattage rule is only a rule as in the turn over rate for circulation or amount of live rock is a rule. It is just a broad generalization (guide line) that has stuck. If you would go to the GARF site
http://www.garf.org you would find they have several tanks set up with just NO fluorescent with SPS growing in them. They use a two part calcium supplement and regular water changes. They set the tanks up to specifically show that Reefing doesn't necessitate one spend a fortune on your tank set up. It is probably a great recommendation to place your SPS in the top half of your tank with your limited lighting, but if you keep your water parameters stable and do regular water changes SPS should do fine with your lights. There are some SPS that actually do better under moderate lighting. Acroporas: Divericata and Granulosa (both from depths of over 40 meters), which require 1/4 to 1/3 the light of most SPS, and Monipora Tuberculosa which requires 1/2 the lighting of other montis, and 1/3 the light of the light loving SPS. I am not suggesting these are the only SPS you can keep, just trying to maybe dispel a little of the Mith that all SPS corals require strong lighting.
