The Umbee will get 20+ inches. Even with the "new tank" that is 24" this will not be easy on him. Get rid of the Umbee.
The silver dollars will just get thrashed in that set up. Get rid of them.
I love Midas, but in this case get rid of him also.
In the 3-5" category all these guys may temporarily work, but when these fish start to reach sexual maturity, you are looking at a war zone. You still need to decrease even more.