Teizman,

If the metal plate is not connected tightly to the medium then you're
going to create arcing between the two. Water is a great conductor and
the electricity will arc, without producing a visible jump.

When electricity jumps like this the amperage increases, with increased
amps comes higher temps and various forms of electrolytic action.
Basically, you're arc welding your connecting plate away.

As for running at 100%, I've never used this unit but would imagine that
it's not designed to work at that level for extended periods of time. I
would strongly recommend that you contact the manufacturer and inquire
further with them concerning proper operation of their unit in your tank
setup.

mark h