Hi welcome to AA!
I'm not very familiar with some of the fish you have and I can't help much regarding filters so I'll let someone answer those questions.
However regarding using aquarium salts, this is something that aquarists are divided on...
Here are some of the pros and cons regarding the use of aquarium salts in a freshwater setup that I can think of off the top oft head:
- Some people use aquarium salts as a one off to help treat sick fish, for example it is common for people to treat ich by using salts and raising the water temperature to speed up the life cycle.
- some people use aquarium salts all the time as a preventative as it is believed by some that it a number of parasites don't like salt water and as such it lowers the risk of having sick fish.
- some people believe that there is absolutely no need for aquarium salts in a freshwater set up because these are after all 'freshwater fish'.
- some say that using aquarium salts puts fish under unnecessary stress and as such the salts should not be used unless you are treating your fish for something.
- other people say aquarium salts are just another commercial product to get you to spend your money and people are basically advised by the lfs
to use it as a 'tonic' when anything is wrong with your fish to make you feel like you can do something for them even if there isn't anyway of saving them
- others say that aquarium salts don't really do much in the ratios prescribed, it's too weak to have any benefits
- some fish are very sensitive and salts should not be used with them
- freshwater fish will be fine without aquarium salts they are not absolutely necessary, in the wild these fish are not exposed to brackish water.
- there will still be people who swear by aquarium salts
I hope that provides you with somethings to consider when making your decision.
Personally I have had successful healthy aquariums with and without aquarium salts.