Lorraine,
About a week ago, there was another thread about salt. It had a funny name, like "Question???" ... see if you can find it. Good info in there.
A year ago, I enlarged my pond, changed over to a bog filter, and followed our local pond store's recommendations for salt, being 1lb per 100 gallons. Shortly after that, virtually all of my plants died, and the bog filter never worked well, either. I blamed it all on the bog filter, as that was the only difference I could think of between the original pond and the expanded pond.
After reading the salt thread a week or so ago, I am convinced that my problems were most likely caused by too much salt. So, even though I again enlarged my pond this past March, yesterday, I drained the whole 1000 gallons and got rid of ALL the "salty" water, replacing it with clean, fresh, un-salted water.
It's only been 12 hours, but I am anxiously awaiting the results... I am betting my plants come back, and my fish will thrive.
Oh, also, I spent Saturday at the pond store's Garden Party, with vendors and seminars. I asked both the plant guy and then the koi expert about salt. It seems salt is NOT really recommended, except as a TREATMENT for problems. If there is no problem, don't use salt. Also, if you have plants, salt is damaging to many, many varieties of plants.