T-5 HOs (no need to be overdriven) with the BTA in the middle or anywhere else should be fine in a 55 w 4-bulbs. The Grimreefer has an excellent thread on the equipment forum where he answers most question regarding which bulbs provide the greatest PAR, how long to use the bulbs, what kinds of animals can be kept successfully with T-5s, etc. So for more specific information regarding the best bulb combos, I suggest you go to that thread. However, I can assure you, 4 T-5s over a 55 gallon will provide ample light for a BTA. For a carpet, I would wonder if it is gigantea or haddoni? For haddoni in a typical 55 gallon, almost certainly. For gigantea, perhaps if the anemone is directly under the bulbs and in the top third of the tank. I expect it would be fine, but I defer the the Grimreefer on that. If you can't find specific answers to whether gigantea will thrive under 4 T-5s, then post a question. He is quick to respond and knowledgeable about specific species lighting requirements.