i have an indoor koi poi pond in my screened in porch. there are no plants in the pond, which is about 25 feet long by 3 feet wide. i'm having a problem with some flying insect, that might be a midge but i'm not sure. it is whitish in color and flies much like a gnat. does not bite. they seem to be multiplying. have tried mosquito dunks in the past but i don't think these pests are breeding in my water as my pond has remarkable water flow. is there a safe insecticide i can use to get rid of these pests? thank you.
By definition, a true insecticide is not safe. Adult midges or gnats can come out of ponds in big clouds. The larvae will be living in the areas where you have moving water, where the koi can't get to them. Look in your filter, filter output, waterfall if you have one, etc. for the little guys. Mosquito dunks with Bt will kill the aquatic larvae of some insects but perhaps not all.
As far as reducing the numbers of adults, you could just wait a few days as the adults only live but a few days before laying eggs or dying. Of course, if you have a breeding population, more will just come out. You can also try to trap them using various bug traps. There are ones that zap bugs or attract them to something sweet or use glue. The glue traps are sold with the supplies for house plants to catch white flies but they'll catch any bug that flies into them. Many species of midge don't even eat as adults since they live for such a short time as adults. Other species will eat nectar so a trap with sugar or nectar might work for them. It's too bad you can't put a few bats in there! In the spring and again in the fall, we get clouds of midges. They don't even have to be near the water since they move around. When I walk through those, I get gnats all over my clothes and end up eating a few! They're a pain but harmless. Good luck!