If u know how to diy pipings, google diy overflow pipe.
Seriously if u want to come into this hobby, make sure your tank is set up the right way. A sump tank will save u alot of problem in the future.
Not too sure about this. My own observation is when the KH went under 7.. The PE suffer but no issue if it is like 9 or 10.
So for me is low KH, i got shorter PE..