I've marked where I found the leak in tank #1 with some tape.
I'm still looking for the leak in tank #2 which leaks much slower.
I found this leak by using soapy water on a paint brush and watching
for bubles.
I'm not sure how to fix it. My hand doesn't fit through the filler neck.
I've thought about cutting an access hole in the back of the tank that
would then have to be sealed.
Another idea is to make a metal piece that would wrap around the
leak flange, and fill this with proseal.