>>2942648
why don't you gift them some mosquito poison tablets for the pool instead? Look for "Bti" in the ingredients. Its used to genocide those pesky mosquitos so hard in my place that environmentalists are very scared as other animals need them as food but we do know now that it is very safe and very effective against mosquitos.
Even if the water in the pool is safe for the fish for a while, i think its a terrible environment for the them long term and is sorta cruel to be honest.