I have two questions if you don't mind
1st What should the salt content be in a pond with plants but still to aid in protecting the fish. Can I get this answer two ways how should a digital meter read 0.00 also what % should it be. My second question is; should I leave my filter running in the winter or get a floating heater and keep a airpump going and turn off the filter. I live in Quenns new York so the winters can be pretty cold.

Robert

Answer in two parts: You really cannot maintain any really 'therapeutic' level of salt in ponds with plants - or the plants will wither and start to die off. The minimum level that matters to fish is 0.3% and this is a level sufficient to hurt a good number of plants.
The digital meter, if registering in percents, would read 0.3% -
Second question - Yes, leave the filter running in winter so it doesn't freeze and crack -
otherwise, it will need to be drained completely and the media (matting, springflo, etc. cast to the bottom of the pond so the beneficial bacteria don't die off.
Leaving the filter running is good but try to not disturb the very bottom [deepest] layer of water, and don't run the waterfalls, or the water will climb and fall in temperature and cause vulnerability in the fish to secondary diseases.
Doc Johnson