Bluecarpet, first off, you have inaquedate lighting. If you were "experienced" with anemones, you would clearly know your lighting is not fullfilling. Although, you did say you have a lagoon. What kind of lighting are you running over that? I would love to see pictures of your lagoon and know what else you have in there with it? At least lets see a picture of a full shot lagoon just to get an idea of what wer're looking at.
In your different statements, you sound very cocky and confident, almost to confident. I am not trying to sound condescending nor inflammatory I am trying to benefit you and the anemone. Even a 24 gallon is not reasonable as you said thats its next tank when it gets too big. This anemone is too aggressive and gets to big for that size tank. And you said "time is on my side, yes it is," well actually no its not. Definately not. Your tank is to small, not good enough lighting. And from what I can tell by the pictures, you have a film on your water surface. Thats not good. What kind of water are you using? Tap, well, or RO water?What I can see that red mushroom in the back does not look in good shape. If a mushroom is not in good shape, well good luck with your anemone. Don't be naive Bluecarpet, do something to help your anemone because your proving no one wrong, your mind just thinks that.