Heya!
75 Gallons is 280L yes?
I have 2 very large Bala (or Silver) Sharks in my 550L Tank.
I would say the bigger the tank, the better, as they are quite active, and grow very large!
Mine are about 30cm now, and are only about 2 years old.
The Balantiocheilus melanopterus or Bala/Silver shark grows to about 40cm for males, females smaller.
Recommended Tank size is 500L.
They have been known to live for 10+ years, good jumpers and can be easily spooked and can hurt themselves, even known to knock themselves out!
Mine eat: Liver/Pellets/Flake and Cichlid Food.

Hope that helps abit?

Cheers!

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