I am trying to build an arduino controlled misting system, but I am not sure what pump I should use. Right now I am thinking of using an aquarium pump hooked up to a relay, but I am not sure if that is the simplest solution. I am hoping to use one pump to power several standard garden misting nozzles (8 - 12) so I think I need a relatively high pressure pump. Any ideas?
An aquarium pump for an indoor aquarium is for air.
You need a normal garden water pump. Every large garden shop should have those.
Assuming 12V power you want a diaphragm pump like these: on demand pump shurflo for sale | eBay
Eight nozzles suggests you'll need something around a 2GPM pump. 40 PSI should work though. The pressure of these pumps is adjustable but you still want to match the flow and pressure as closely as possible to prevent the pump from turning on/off rapidly.