Well my 180 will soon be empty as my RTC is going in the pool as soon as I can get water conditions and everything stable so what ever I get will pretty much have the tank to its self
If this is the case you could have a jardini and try and raise it with tankmates from a smaller age to try keep aggresion down to a min in future (im currently doing this with a 6"jar with the one thing my old jar hated with a passion "silver fish" so he's in with tinfoils atm), your saving grace is you've got space both in the 180 for growout then in your pond eventually
My first aro was a silver but once I got a jardini I never looked back there quality fish if you can train them to feed on pellet and play nice

, obviously thats only my opinion you may love silvers like I love jardini