Since you've had two anemones die in your tank and you aren't exactly sure why, you really should figure out what the problem is before getting another one, or it will suffer the same fate. If you just had a standard NO lighting that came with the tank, and the anemone died after 4 - 5 months, it is quite likely that the lack of lighting caused its death. Despite the fact that you upgraded your lights for the second one, 110W over a 55G tank is just 2 watts per gallon, which is not strong enough for most anemones. So lack of lighting may be what killed your second anemone also. You say you think it was water conditions, how did you come to this conclusion? Did you test your water and find high levels of ammonia or nitrites? If you do plan to get another anemone, as others have said, a BTA would work out best. However, IMO you need to make sure your water parameters are stable and you should at least double your lighting before getting one.