Since spotting that first wriggle in the peat yesterday evening I have been back to check on the hatching tray 4 times, and each time have been unable to resist the temptation to stick a podgy finger into the water and stir it up a bit so that I can see which tiny specks are able to propel themselves against the current.
They really are minute. Much smaller than most of the peat fragments, and more or less transparent too, which makes them even more difficult to spot. There's a marked difference in size even amongst the fry that have hatched within hours of each other. Dunno if that means some of them came from smaller eggs, or if I couldn't spot the smallest ones until I'd seen a few of the slightly bigger ones and recognised the movements.
Poor doomed little fishlettes, born with only a tiny supply of nutrients and forced to swim off all their stored food supply by the evil fat finger of death. I vow not to poke or prod them again for at least 24 hours, and only to drop a couple of drops of baby brine shrimp into their tray later on this evening. Benign neglect, how hard can it be?