Is there a way to better seal the tank? *My grinder has a 40 gal tank and I
don't get any evaporation but we have to add a preservative or it gets
stinky.

Hmm, not really the tank is pretty well sealed in the machine base,
probably 30+ gallons. The evaporation must be happening on the table
as that's the only time the fluid is exposed. The table drains have
hoses that take it straight back to the sump. We almost never have
overflowing into the base tray.

As for stinky, try using a fish-tank bubble from a pet store. It
oxygenates the water and stops the bacteria stagnating. Have not had
to use "the pill" for years.

Dave