Ok, hope this will help...
Feed jar until it wont receive any more food..
then you can put the marbles in.
In my case, aro will go and do some manuvers near / on top of the rays,
but since it's very full , it wont even bother to open its jaw to attack the ray.
This will last a whole day and then aro will lose interest in the ray..
Keep in mind to always feed your aro until its fullest, at least for a day or two,
then you can go back to whatever routine you have.
Anyway, its just my experience, so you should keep an eye for any actions happening in the tank and get another tank ready for separation.
My worst scenario now is having a serious drop eye on the aro
