I’m going to use the 100gal stock tank as a sump directly behind tank. With that setup I did the plumbing pretty easy. I’m gonna run the old sump as another tank in the system and can plumb that in after stock tank in place. I’ll trim the full siphon right below waterline once it’s all setup. I left it long for now. I’m just gonna run one return line. I capped the other one off of I ever feel like using it in future. I may plumb the UV through it independently. Would also give me a backup return from sump if either one were to fail.