These guys require some params that closer match my crystal shrimp than neos. I would keep them in no less than 8 to allow them to shoal comfortably. If they leaped, there was likely something amiss in the parameters. Listed below for reference.
Size: 2.5 cm / 1 inch
Temperature: 75 - 79°F/24 - 26°C
Hardness: 1 - 5°H
Yeah, I think they jumped because the params got out of whack when I neglected the tank. But I'll be keeping a watch on the water now that I restarted my tank and I'm going full EI dosing. Would 15 be a good number? They'll be the only fauna in the tank, except for an oto and some snails.