MICROBE-LIFT BMC Biological Mosquito Control, Liquid Treatment for Medium-Sized Decorative Water Gardens Up to 2,000 Gallons, Fountains and Ponds, 6 Fluid Ounces

No, use this or any product with this ingredient. 100% safe for millipedes. https://a.co/d/01rgfZwZ

the water you use could be mixed with mosquito bits (works for gnats) or the liquid version ( https://a.co/d/0hWXK034 ). can take a week or so to see results but it works. fruit fly traps ( here also help, put these around your bins. Zero Flying Insect Traps seem to catch a good amount for us as well. when making ventilation holes you should either get plug ins with fine mesh ventilation or cut a sheet of sieve cloth, cheese cloth, something like that to prevent gnats going in and out. letting the top layer of substrate to dry just a bit more should help without hurting the isopods too, at least until things get better