My suggestions will always be large wrasses in a large fowlr.
Unfortunately in australia my choices are limited, (after waiting for 3 months, i finally got ahold of a male paddlefin wrasse for a meager $550 which is a 6x markup from their price in the us) but if i lived in the US these would be my picks
1: Male Thalassoma genivittatum. Commonly about 5-7inches and well behaved for a Thalassoma. On the rare side but not overly expensive in the US. This is my personal favourite fish ever. Hopefully in the next 5 years one will be imported into australia and wil be less than $1000 :(
Newtons wrasse, Thalassoma newtoni
A small species of Thalassoma that doesn't often get larger than 6" even as a mature male. The blue facial lines are gorgeous. Commonly available at live aquaria
Another suggestion is a male Paddlefin wrasse. They might be the second most gorgeous wrasse in my opinion. Females look nice too but are small usually. Males also commonly 5-7". On the aggressive side of Thalassoma but nothing too bad.
Coris atlantica is another gorgeous wrasse. Coris gaimard, Coris formosa and Coris aygula get all the love in large tanks but these guys don't seem as popular for some reason. They're often available on liveaquaria. Can reach like 8" or so in captivity but often sold smaller. Coris have a reputation for being aggressive but that hasn't been the case, all of mine are model citizens.
And if it were my tank i'd round up the coris and thalassoma squad nicely with one or both of these gorgeous species
Both reach 7-8" in captivity and sold at a variety of sizes. Both species are extremely active and should be classed as sort of 'boisterous', but unlike most other boisterous wrasses completely non aggressive in my experience. But they aren't afraid to steal food off other fish. I had a 4" spanish hog in my tank a while back ($400 in australia!) and it was one of my favourite fish ever and the last surviving fish as the tank crashed. Cubans aren't quite as nicely coloured in my opinion, the purple on spanishes is just unmatched but they have a sleeker shape with nice long streamers as they age.
Anyways, i think you could have a lot more fish without that stingray in there. I don't know much about them but i'd be concerned they would eat fish and i've heard they need absolutely enormous tanks with minimal rockwork. But who knows.