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5 gal is suitable for 8 celestial pearl danios, a betta, or shrimp and snails and that's about it, most all tetras are extremely active and need/prefer atleast 20" of swimming space.
Remember the 1 inch per gallon rule. Neon tetras grow to about 1 1/2 inch long, so I would have maybe 4 max. I wouldn't put male betas with other fish.