Here's a pic of the all males I got from Matt's 55 gallon.
Since then, added 11-12 fish large and small. The survial rate is around 80%. I think it depends on the personality of the fish. The 3 or 4 that I lost were shy from day one.
A little orange guy (top left) actually got stucked in the mouth of the dominant cobalt and has its tail half bitten up by others. I thought it was a goner. He was spitted out next days and is strong and growing fast.
There is one female cobalt in there. It bred and there is still a small fry there probably 5 weeks old.