As bruinsbro1997 said .. a 30gal is too small for an RTBS due to their territorial aggression as well as a pleco (assuming common pleco) Neons should do ok with TigerBarbs ... they're small and fast enough to simply avoid them. Cardinal Tetras are another tetra option ... but one of the best tetra options I've heard/read about are Serpea Tetras.
Keep in mind ... Danios come in various colors ... not just the zebra which is the most common found in LFS
's. But blue, leopard and glofish danios are just some options ... but a 5 gal
is too small for such active fish.
75g Planted Barbs Denison, BlackRuby, Tiger, Albino Tiger, Green Tiger, Cherry, Gold, Checkered, Odessa.
NonBarbs Cardinal, Neon, RummyNose, Bloodfin Tetras, Z. Danios. 1RTS. Amano, Bamboo, Ghost & RCS. 20g Long Shrimp Tank RCS, Tiger, Amano.