Each egg raft can hatch 100-200 really tiny mosquitoes. These are a whole lot smaller and softer than the newest hatched baby brine shrimp. They are essential food for very small newborn fish such as gouramis, Bettas, rainbowfish or lampeyes. (Just because a fry is 50 mm long doesn't mean that it's mouth is all that large.)

The mosquito larvae will filter feed "stuff" from the tank and grow until eaten. After a week or so they could eat a baby Betta, so one should keep an eye on them.

But... it is handy to bring some rafts in and dump them in a container of water from a healthy tank. They will begin hatching within hours. A turkey baster load into a tank of fry will hold them a day or more.

Outside one can simply slide a finger under the raft. If done gently, surface tension will draw the raft to one's finger. The rafts are flicked into a contain (yogurt cups work) and carried in to be briefly refrigerated, frozen or fed to fry.

Interestingly, not all eggs will hatch at once. Presumably in nature, if there is not sufficient water to allow a generation to grow up, there may be eggs to hatch later.

On out-of-town weekends, the rafts can simply be tossed into the fry tanks. They will be browsed upon as they hatch. (Be aware of the fact that snails will eat them.)

In this age of scary mosquito born diseases, there is a moral obligation to harvest those eggs or mosquitoes before they go through a metamorphous into adults, bite someone (or more likely an animal) with something like the West Nile Virus and spread the "blessing."

As I've tried to explain to our neighbors, having them lay their eggs where they will be harvested (by me or the hungry Daphnia beneath them) means that those are eggs not laid out in the woods where they will grow up to plague us.