Advice On New Hap Tank

[teddyman5]

Looking to turn one of my tanks (300 litre) over to a hap tank. Want something very colourful. Tank has an internal and a Fluval 405.
I have kept fish for 35 years but never these so looking for advice on how to keep water chemistry correct (salt mix?) , what substrate and decor, and what fish and how many, all suggestions gratefully received as at present I am looking for ideas.
Thanks a lot

 

[peachlids]

my inexperienced input, from what i have seen, black sand substrate looks awesome with a dark backdrop, im a fan of lava rocks and slate, and keeping my plants to a minimum but live plants. i also ended up buying cichlid premixed bio substrate crushed shell and sand mix which helps get the ph where they like it