Flow flow flow...
Once you know you have the right wattage... your sebae needs a moderate amount of flow... some even like it heavier... it'll attach itself wherever it is happiest in the tank, but you can help it to make that choice (say you don't want it to be in the back behind that big rock that no one can see around) by giving a good 3-way current. That would be... one powerhead or other pump in the back of the tank shooting water to the front... and two more, one on either side of the front of the tank, shooting water towards the middle of the tank.
something to keep in mind... the longest any sebae has survived in captivity is 6 months. And that's with a Marine Biologist taking care of it..
The hardier and (IMHO
) better anemonies (that you might want to try after the Sebae experience) are Hatian purple tips, long tenticle, atlantic rock and bubbletip/Ritteri (although some bubbletips, like the Rose, can be VERY expensive and slightly more delicate). Almost all of those you can find at an LFS
that specialises in saltwater.