Some people use salt in their tank regularly, others say don't do it becasue it is not natural. There is no constant advice on this one, assuming your fisn can handle it. Other people, like myself, use salt to help the fish when stressed or sick. The main fish that can't handle salt are scaleless fish, especially catfish species, which you don't have. But you may want to do some research, or maybe someone else can answer definitavely. (You can also try posting on the board for specific species).
OK if you decide to keep salt in your tank on a regular basis, there are a few things you need to pay attention to. The first is evaporation. Salt will not evaporate with the water, it stays behind in the tank. So when your water level decreases, you have a higher concentration of salt. I would not recomend using salt long term if alot of water tends to evaporate out of your tank.
The only way salt will leave your tank is if you take it out through water changes. So if you want to keep salt in your tank, add back in the amount of salt you removed. For example, I have a 20 gal tank, and do a 25% water change weekly. So If I had salt in my tank on a regular basis, i would add back in the salt for the five gallons of water, not completely redose the tank. Make sense?