For me this is a significant consideration with these shallow tanks - I have ADA 45F and ADA 60F and have never managed to convince myself to place fish in these tanks once scaped: the tank height becomes just too shallow once substrate, hardscape etc are in, and water volume is correspondingly reduced
While the various microrasbora species are very small, they are also substantially timid fish (keeping in groups of at least 30 helps) and I wouldn’t keep them in such a narrow shallow tank (despite a group of 30 “fitting” into a tiny space)
Shrimp can do very well in these tanks - though I’d add some floating plants (and a cover for several weeks to eliminate escapees, once settled they’re much less likely to go exploring)
A single domestic Betta splendens or possibly a (suitable) group of some of the smaller wild Betta species (but then specific water parameters and a tight fitting tank cover are required)
You could try some endler (especially endler guppy hybrids are very colourful) or smaller guppy types (some of these “dwarf” guppies are endler hybrids but bred to maintain more guppy traits) - these are generally colourful active relatively bold fish, though I’d only keep males re small size and not wanting multitudes
Note that many of the highly bred guppy types have limited fertility, and smaller size including females so could be an interesting fish to keep (my experience is with Asian guppy lines)
Aquarium Glaser Endler
There are many more types, I just link AG re Frank Schafer’s amazing photos
(he has also done many guppy photos)
Even when adding guppy types to this tank (which are not known jumpers), I would include a glass top especially for the first weeks (while fish “learn” the tank space), floating plants or overhanging stem plants etc will also tend to minimize “jumping” (which is often a startle reflex)