Adult mosquito shouldn't be fed to the betta unless you are breeding/raising yourself.. but if caught outdoors then not ideal as no one can know what they had fed on previously. You can easily transfer viruses, infections to not only your fish, but to yourself as well by using adult mosquito-
Use the larvae, in a bucket with leaves and branches in it.. scoop them out with a shrimp net, gently rinse them off and feed.. leaving the adults alone to breed more.
Just too great of a risk feeding adult insects that are commonly carrying around infectious diseases and normally tend to have something that could easily be deadly to the fish.. and yourself.
Adult flies and gnats do most of their eating in piles of.. well.. poo. Which can also consist of viruses and diseases. Always best to just use a bucket and use mosquito and daphnia larvae which have yet to be exposed to the dangers of adult insects.
(If it happens by accident, which can and mine have snacked on something here and there that dropped into the tank thinking it was going to be a simple drink.. don't sweat it too much.. but in general it's best to know what exactly you are feeding them and try to make it the safest as possible)
Last edited by Myates; 02-16-2012 at 05:17 PM.