Looking At Getting A Pitbull Plec Lda25

[ant0]

Tank size - 60 litres 15 US gallons got the following:

9X neon tetra
2X molly
1X guppy
1X shrimp

I'm looking at getting a few of these, would 3 be ideal as they only get about 5cm?

Tank has been going for 2 months and is my first tank. I've recently put some sand in but its mostly fine gravel and there is driftwood, places to hide and quite a few plants

PH = 7.5. Water is hard and nitrates are always low. Will this be a good addition to my tank?

Thanks