Happy Birthday Lionel, working here on the present you want to get yourself!
I guess Ivan just wanted to make things more mysterious filming altums in the pitch of dark... I hate going into rivers or any water body, even a dang pool for the fact, at night... a bad experience way back.
The fish at 19 m most likely belong to genus Hemigrammus, probably H. marginatus or a close species... but it´s hard to precise, they move too fast. There are a number of these species that are closely related or have slight variations. If they are H. marginatus, they pick up a nice rich yellow coloration in the caudal, dorsal and anal fin when ready to breed and (in Venezuela) we call them "sardinita amarilla" o "sardinita dorada", which means yellow or golden sardine. I think they are called Gold or Golden Tetras commercially.
God listens. He may not always give you everything you want, when you want it; but he always gives you what you really need, when you need it most!