Used a brass check valve, didn't go well.

[Clooney]

I just moved everything from my old tank into a new one that I built about 2 weeks ago, The old tank was 2 years old and all I did was move the water, rock and sand into the new tank because they were the same size just different shapes. Tested the parameters cause I thought maybe the tank started to cycle again or something like that but nothing out of the ordinary there. Then last night I was researching brass in aquariums and found out your not supposed to do that. Reason for a check valve was I drilled the hole for the return just below the water line so I was nervous about back flow. I'm going to grab some loc line today to bring it above the line to avoid the need for a valve.