PS4 Help with banner farm.

[LeftyRedd]

So I've been trying to get a Nymph Banner for the longest time and decided to do a AFK banner farm that I saw online. But 20 minutes or so after starting it, barely any enemies spawn. Was wondering how to fix this because I want to leave it running without input from me.

 

[salad_den]

use lizard bricks and a water candle or the official terraria gamepedia for more help