Most black fish?

[Chicxulub]

It's not all black, but its hard to beat the black devil for cool factor

 

[Gourami Swami]

Paratilapia polleni with a school of black mollies, would be pretty damn impressive

I would be careful of going too light on the substrate for a public tank, algae will show a lot. Might be better to go with brown substrate so the diatoms blend in and it doesn't look dirty

 

[Muni]

For that size tank you could maybe do black and white fish like convicts with a slightly darker substrate to hide algae growth.

 

[phreeflow]

Polleni, double dark black angelfish, and black ghost knife would look awesome

 

[white specter crayfish]

Probably won't work for you but a ripsaw catfish

 

[Mitchell The Monster]

Black Angels? Compatible with your original community type fish. You could do a tank of tropheus duboisi. Black with white spots when young and get a big, bright yellow bar in the middle of them into adulthood.

 

[Backfromthedead]

Multitude of black oranda goldfish.

 

[justarn]

Black ranchu

 

[KansasSunfish]

Polleni, double dark black angelfish, and black ghost knife would look awesome

I forgot about black angels! Wouldn’t do well with a ghost knife though

 

[KansasSunfish]

Black Angels? Compatible with your original community type fish. You could do a tank of tropheus duboisi. Black with white spots when young and get a big, bright yellow bar in the middle of them into adulthood.

Definetly black angels. This is got me thinking that maybe I should do a school platinum angels with one black angel fish. Then I can go a bit darker with the substrate and I think the black fish with stand out a lot.