First off, it's not the number of watts on your tank, it's the quality. Putting 4x24W T5 bulbs over a 23 gallon tank is likely enough for a RBTA or BTA. Total watts = 96 watts, but if you put 2 60watt incandescent light bulbs (=120 watts) you probably won't be able to keep much of anything in there. See the difference? Quality vs. Quantity. Don't let anyone give you a "watts-per-gallon" lecture, too many variables for this inaccurate "rule-of-thumb" to work. Now, your tank is on the smaller size, so you could get away with a smaller bubble-tip anemone (provided your water quality is sufficient). Be careful with any powerheads/intakes in the tank. It's a small tank and if the nem starts moving there's not much room before it hits a powerhead.