What kind of fish/invertebrate can fit in a 5.5 gallon FOWLR tank?

[homersimpsonlikesfish]

What kind of fish/invertebrate can fit in a 5.5 gallon FOWLR tank? I am planning on building a custom stand that can hold up to (4) 5.5 gallon tanks. I just like the small and compact size of a 5.5 gallon tank that is easier to do water changes.

 

[Doctorgori]

-mantis shrimp might be amusing…
- a pair of neon/sharknose gobies with careful planing/water quality
- skunk cleaner shrimp
- clown goby
- masked goby