the water is from a well, shallow point which means it's abt 5 to 7 meters deep at best. as for sewage you could be right I do have a septic tank out here. the only decorations I have is a couple ceramic? hollow logs I bought at the fish store. the fish are 2 angels, 2 cory cats, 2 clown loaches, 4 platys, 6 harlequen rasboras . The angles are the oldest apx 6 months