Your water parameters are fine. I maintained a pair of these interesting fish for years in a tank with very soft (zero GH and KH) and acidic water.
Jumping out was the biggest problem; they will readily jump and the tank must be well covered.
And they will eat, or attempt to eat, any fish that approaches the surface. And as they have very large mouths (the whole jaw drops) they can handle full-grown neons.
They need lots of floating plants, with sufficient space in between for them to rest at the surface. They swim very little, usually only to "hunt" for food. They are a true ambush predator, sitting motionless for hours.
A pair wold be better than a single fish, as they will interact more. Distinguishing male and female is relative simple; the anal fin of the male is longer and has a distinct notch in it, whereas the female's is basically round. I strongly recommend a pair.
Something as small as a 15g works, though a 20 long would be ideal; as I mentioned, they are not much for swimming, except when feeding or interacting. Quite a fascinating fish.