I think you should get the other fish out as soon as possible. Mine has always seemed to go through phases where he doesn't bother other residents then he -can't- because there AREN'T any more residents.. Seems to be growth spurt related. He still has some glass cats living with him but they've learned to avoid him when he starts patrolling bottom to top.
He also paralyzed a weather loach and waited a full month before suddely eating him and the other loach in the same night. A school of 8 adult silver tip tetras lasted a week (he was only 4") and then 6 were gone one morning.
A synodontis petricola lived with him for nearly a year and grew from and inch or less to near 4", used to follow him around, sleep in the Ecat's cave and everything, then just gone.
Sometimes he'll leave guppies alone for a week or two then eat dozens overnight.
Seriously, don't trust him with anything you aren't okay with being fish food.
BTW, when I still thought he might be able to have tankmates I tried overfeeding him, he just pooped more, they still get eaten.
*edit -I have heard semi-succesful stories with african cichlids, makes sense, but none others long term. They still get shocked and occasionally eaten.