Hello, I have a waterbox cube 20 AIO aquarium. I have lately been having problems with keeping the return chamber filled. I do not believe that it is because of evaporation because I will fill up the third chamber with water, and in a few hours it will have completely drained it out. I have changed out filter socks and removed media from the middle chamber thinking they were slowing the flow but that did not fix anything. So I am stuck at what else to try to fix it.