Welcome to the WC bigfin. Excellent info here to help ya every step and beyond with your new set-up.

166g, giddy up. The Giant Danios make a great dither, Ive got a school in my 75g, with a tank your size you could get a big school of them if you wanted, like 10-12 or so. They are real fast, will swim you dizzy until they settle in a bit. they only grow to 4-5" so thats why i said you could add so many if you wanted to, would make a cool "big school".
With 166g you could also go the larger dither options like Silver Dollars and Tinfoils Barbs. Both are school fish, both will grow big so a smaller pack, but good mates for big cichlids if you have the room. The SDs i think grow to bout 8ish", and the Tinfoil Barbs can top out BIG, like 11ish", so fewer of them. maybe 7 SDs or 4-5 Tinfoils in a tank that size.
These numbers arent "scientific" by any means

just some thoughts for ya cause a good school of fish roaming around really adds to a tank I think, and they will clean up alot of extra food bits that messy cichlid will "spill" plenty

(ramblin

)- again, welcome to the WC 1BigFin.