Unless you have a really good system its best to go with a BTA for clowns. They can multiply and they can move. I'm not saying they are easy to care for but I keep my RBTA anemone in a 36 bowfront with no skimmer or filter. I do have a HOB refugium, dual 150 MH 14000k lamps. and dual BoodsLED par 30 with 4x royal blues and 1x white in each bulb.
Light and stability are the two main things I've found to keep an anemone alive. Keeping nitrates at around 5 ppm seems to work great also. Anemone absorb the water and feed from the nitrates in it. You do not want your nitrates to be more than 10 PPM though.
The biggest challenge I've had with them is keeping them past a 2 week mark. At 2 weeks, it's often shown to be thriving or dieing. With a 55 gallon tank, you should be fine with a BTA but what gets me is your mention of 4 t5 bulbs. Some people claim to keep anemone in low t5 light but with just the dual 150w halides on my 36 gallon tank, my RBTA shows a lot of browning which was my main reason for adding the BoostLED par30 bulbs.
I needed some serious actinic as well as more light that the halides were giving. I've also got 48 cheap 470 nm leds on the tank that really don't put out a whole lot of light but really make for a nice bright night lighting. Between the BoostLEDs, the two strips of 470 nm leds, and the 14000k metal halides, my tank looks prismatic as well as awe inspiring. Damn shame I haven't got the camera to capture the color.
I've tried keeping long tentacle and BTA under quad t5 on both my 36 gallon and my 20L only to watch the anemone quickly fade away. If you want to get a BTA then double check all your parameters and if you have any second guesses about something being off they don't get the anemone.
Nitrate below 10 ppm ideally 5 ppm and controlled. if you try to maintain it at 5 ppm and it shifts, it is much better to shift to 1 ppm than it is to shift to 11 ppm. If you think you may need more light then you most likely do. Be sure your water is clean. Skimmer will take food from your coral and anemone so the way I stand is to do without the skimmer or simply turn the skimmer down so it collects less.
My favorite is a tank full of filter feeders. All the filter feeders along with a large amount of live rock really go a long way to giving me clean water. Last but not least. Frozen mysid are your best friend. Live mysid and the anemone would be in heaven. Maybe one other thing. Anemone get stressed easy enough as it is, don't be afraid to take some extra time acclimating it. Anymore, I will always drip acclimate my anemone for as long as my time permits in a room where the temperature is close to 79 degree.
Sorry If I just rambled on to much about it but the short is, as long as your parameters are right where they need to be, the lighting is good, you feed it what it wants to eat, and acclimate it really good, you have a good chance of the anemone making it past the two week point. If happy then, they usually remain happy unless you start letting things get out of whack.
