I would go with something other than neon tetra they are small fish for 55 gallonf JMO. The barbs i had were not nippy on other fish, they were the most active of my tank till i put soap in the tank by mistake. I only had one red tail and he left others alone, i also had albino rainbow shark with him. I like the red tail only because i had one as a kid, when i get my 55 gallon i might get another red tail to keep in my 29 gallon? I would really stay away from the neon tetras and go with the gourmai idea, they are beautiful species and would look nice in big tank i think.