With an anemone in a 24" deep tank a 400 watt HQI Halide center light would not be too much light, so that pretty much puts you at least in the three 250 watt HQI halide range. The cost is steep but the 72" Outer Orbit Pro Series with three 250 Watt HQI, eight 39 watt T-5's and 24 moon lights is a great light, but the price is $1100. The comparable light in PAR to that light is the Aqualight Pro at a price that is $400 dollars higher in price and 72 watts more lighting, not including moonlights, but they use three 250 watt HQI halides and Power PC's instead of T-5's. The Reflectors are better on the T-5's so the PAR is a little better, but they are not as good as the good individual reflectors used in the better straight T-5 fixtures. If it were me and I planned on an anemone I would use all retrofit equipment with a 400 watt HQI halide (and place the anemone under this light along with any large acro SPS corals) flanked by two 250 watt HQI halides with 8 39 watt T-5 actinic all in individual reflectors for a total of 1212 watts. I would use all 10000K halides and no moonlights. For your tank to have 1000 watts per square meter shining on its surface that would mean 1195.38 watts. So what I would recommend is just 16.62 watts higher than the average wattage of lighting energy striking the earths surface. Lots of coral see higher lighting than this on clear days, but considering cloudy days and depth factors ans such a 1000 watts per square meter is good figure for estimating lighting needs for shallow water marine organisms. Three 250 watt halides would put you at 133.3 watts short of this level. I personally would not recommend a straight T-5 lighting system for a tank that long, and that deep, that will contain both SPS and especially anemones. As far as replacement times on HQI halides my bulbs 10000K bulbs are not dropping appreciably in PAR until over 16 to 18 months of age, and still have a better PAR at 16 to 18 months than a T-5 bulb that is brand new at a depth of 24 inches. Typically fans will control heat dissipation through the promotion of evaporation which removes great amounts of heat.