What you need to do is a lot of research- your tank should be AT LEAST 6 months goin before adding a nem.
Its NEVER a guarantee that your clowns wil be hosted by the nem you put in.
They are NEVER permanently in 1 spot guaranteed. Just because they find a place theyre happy in at the moment doesnt mean that theyll never move again. They may decide they dont like the flow or light in that spot after a while and move. Theyre animals not plants so they dont "plant" themselves and stay. Mine moved around for alomst 2 weeks, settled in at one spot. Stayed for a month or so then moved again. Has been in the same spot since but ya never know. Also when they split doesnt mean that the one that splits off will stay there either. Im lucky mine split and they both stayed, again lucky is all, I may wake up tomorrow and find either one of them in a different spot.
The biggest thing is also they can and will knock over and/or sting corals as they move about the tank.
You need to make sure when you do put one in the tank that theres no possible way they can get sucked up into your powerhead (dont underestimate their ability to get tentacles and parts of their body sucked into one).
If they die they tend to SERIOUSLY foul your water so be prepared for that.
Heres a great website to do some research on:
www.karensroseanemones.net
Be patient- clowns can live their entire life completely happy without a nem so dont think they wont be just as well off without one as they will with one to be hosted in--just wanted to point out- the nem hosts the clowns, clowns dont host the nem.