Glass Larvae (Chaoborid larvae). Glass larvae may turn up at your LFS in late winter, if there's an enterprising fishkeeper in your neighborhood to collect them. Recently they've been more widely available shipped in those oxygen-breathing clear plastic "sachets." Glass larvae are the overwintering larvae of various species (about fifteen in North America) of phantom midges (Chaoboridae). The non-biting phantom midges are a natural live food for tropical fishes; they're found in all freshwater muddy and sandy sediments throughout the world. Rest assured, phantom midges are not the biting no-see-'ums. Glass larvae are little predators, but harmless to fishes, even larger fry; their prey are rotifers and minute crustacea like copepods and daphnia, and other creatures less than 2 mm, which they grip in their unique modified antennae and swallow whole. Fish are gluttons for glass larvae and can choke on them if you feed them to fish that are too small to handle them. The drifting movement of glass larvae, combined with the rapid twitch they use for evading the fishes, brings every predatory fish instinct to life! Inside the all but transparent larva are two shining beads that look like droplets of mercury: they're air sacs. You may also see small white globular spots, which are encysted sporidean parasites: a problem for the phantom midges, but not transferable to fishes or to you.

Glass larvae are reputed to be perfectly clean and wholesome, but watch out! they may bring dragonfly larvae with them. Float the glass larvae in a white saucer and pick out anything that's not a glass larva. You might want to keep whatever strangers you find in a screened-over glass jar with some plants in it, and see what the interloper turns out to be. It seems to me that, quite often after I have fed glassworms, some fishes will show the signs of gill itch. I'm not sure that there is a connection--— I never add the water the larvae travelled in to the aquarium--— but I'm less enthusiastic about glass larvae than I used to be.

Chaoborid phantom midges mature, mate and lay a raft of eggs in the early summer, all within a single week. The overwintering instar that we feed to fishes is the third of the Chaoborid larval stages. One more transformation and they may start to pupate. The unusually lively pupae are also good fish food, but don't delay. The next instar will be the flying adult. The adult phantom midges are not biters; in fact they scarcely feed at all during their brief adult life. Yeah, but try telling that to the rest of your family, if a cloud of phantom midges come flying out of the refrigerator and start crashing into the light bulbs!