IMO, anemones do NOT belong in tanks, esp with new hobbyists, nothing personal.
Judging from the questins, I am assuming you are fairly new to this(if not sorry), which would lead me to believe that your tank is very young as well. Anemones have very delicate needs, which can only be provided with a mature and established tank, outstanding lighting and the care of experienced hobbyists, and even then, their lifespans are not near what they should be. Some may brag of having one for a year or 2 but this is nothing. Personally I willn ot even talk to anyone who has had one les than a year. I would seek my advice on keeping them from those who have had them for years(if I were to keep one). And this is still not a good measure, since most still only live for several months to a year or 2(they should live for 100s of years)
As for your questions, if your tank is young, Then the odds of it surviving are very slim to start with and this could be part of the problem, but if you want the best answers, give us the infor already asked for.