You can easily, and successfully frag SOME species of anemone.
Ritteri's you CANNOT.
BUT.....BTA's.......you CAN! And I have read other threads here from people that have done it intentionally and had success.
And it is easy too!
I have 2 very large rose bta's.......one day, one of them decided to go for a walk, got sucked (partially) down my overflow. It eventually tore into 4 pieces. All of them lived, and are now growing in my tank. And since then....one of those 4 has since been partially sucked down an over flow...tore in 2 and both pieces survived....they and just smaller anemones now, but they are fine.
Now....11 years ago, when I first got my ritteri.....it wandered and got partially sucked into a powerhead when I was at work. The thing was shooting pieces of anemone out of the front when I walked in the door. I thought wow....this thing will surely die now.
But......i still have it to this day....it is HUGE, healthy and there are absolutley no visible deformities. It grew all its tentacles back, but the pieces that got torn off did not grow into new anemones.
Before my female clarkii clown died (rest her soul, had her for 11 years too) she would get very angry if she had eggs and I came near the tank. She would get mad and bite off tentacles of the anemone and spit them out. When she did it to the ritterri, the pieces would die. But when she did it to one of the roses......it would form into a small anemone....absolutely tiny.........i had some in my tank that were not much bigger than a pencil eraser......now they are the size of a half dollar and growing.
So it can be done..and with bta's....I would say it is done rather easily. One thing I would make sure of......water quality must be tip top or there could be an infection........if that happens....well.....that could lead to a total crash and tank melt down.
Again, the only species I can confirm that it works is BTA's. And it doesnt even need to be a 50/50 split.....just tear a hunk off and it will grow......at least they do here. I started with 2 and now I have at least 10. I know it is 100% fact that BTA's can be forcefully split. Ritterri's I would say with pretty much certainty that they cannot be cut........but I would give your sebae a very good chance of it working.
Please keep u updated!