A pool nozzle that includes an air siphon for injecting air into the pool Jetstream. It uses an overall 0.75in port and is designed for Hayward style 1.62in diameter pool Jet.  Injecting air into the pool can increase PH without additional chemicals.  You'll need a jumbo straw with roughly a 0.4 id for the siphon.  

Print with bed supports and out of something durable like PETG.  designed to not need internal supports since there would be no way to remove them from the venturi cavity.