More of an anemone/clownfish forum question, but I will be happy to help. First off, what kind of anemone is it? If it is the "BTA" then yes, maroons do prefer these anemones. However, they are not one of the preferences of percula clowns. For your size tank, I would not recommend (at all) adding a maroon clown with your perc.
It is a bit small, but judging from the picture, it appears to be Condylactis gigantea--a non "hosting" type, as it is from the atlantic. It is difficult to say whether or not the percs will accept this type of anemone, but I will say that it happens more often than one might think.