Yah I bought this Red Sea killer kit that you feed the aptasia so I ain’t to worried about it, it’s just pretty upsetting that imma have to kill it. Since it flows on its own in the water with its long arms. It’s a really cool creature but it can’t stay if I want cooler corals.Aptasia spreads fast - you will want to remove that ASAP.
The star will most likely wind up being harmless.
Ghost shrimp are great at dying, I wouldn’t sweat it much.
There will always be a drawback for every fish and invert you can get, the trick is just to find the ones most suited for your tank.