Hello; A bit of caution about salt. Many fish need some salt and a lot do fine with some in the water. There are some species that do not tolerate salt well at all. Do a little checking on the fish that you have or plan to get.
Also salt does not leave a tank during evaporation, so once a proper amount is in a tank more will not have to be added. For example if you have a ten gallon tank and have to top it off with a gallon of water you do not have to add any more salt.
At water changes you will only need to add salt for the amount of water changed. Say you siphon out four gallons and put five gallons back, you only need new salt for the four gallons plus a tad. My thinking is the salt concentration in the four gallons removed should be concentrated a bit due to evaporation, so over a lot of water changes the salt concentration will be affected. I do not have any idea how to calculate this. There use to be an insrtrument that measured salt concentrations, I do not know what is used today.
All that said, I do not add salt as a matter of course. Some of my fish do not do do well with it.
I am not aware of any serious impact on biofilters at levels used in freshwater tanks. Others may have better info.