I understand that. Again I will state--there is absolutely NO reason to add salt to a FW tank, especially with fish who prefer soft water.
+1With your comm, the only species I can offer would be Colomesus asellus. They're a true FW species and not as likely to tear tankmates up as would other FW species. These max out at about 5".
My water has a bit of salt
Oh Wow. How Hard is that? You have been extremely helpful and again I would like to say thank you.Keep in mind, the puffer they are recommending is still a nipper. It also has the difficult task of catching & clipping it's teeth every 4-6 months. Worst puffer in the hobby for overgrown teeth.
You should not be using ANY salt with FW fish. I do not suggest puffers at all, in a community tank. Your tank is already fully stocked. Your "shark" & barbs are schooling fish.
No amazon puffer or Colomesus asellusFigure of eight puffer??