Question
We have a 650 to 750 gallon pond with waterfall. At present we have around 20 feeder goldfish of varying sizes and ages. Is this too many? Someone mentioned putting salt in the pond, for what reason? Our fish and plants have always been healthy without it.

Answer
650-700 gallons is enough for that many fish for a year or so.  Once they all are each about 4", you may need to start getting rid of some.  Salt is good for goldfish because it helps their osmoregulation.  Just like humans, a fish's body is comprised mostly of salt water.  The difference is that fish are constantly absorbing and releasing the water around them.  It helps their overall health if this water is close to their bodies' natural salt levels.  Too much salt is bad for plants.