What is the difference between TT filter and baki tower? Which one is better for koi pond?

What are the benefits of bakki shower with koi pond?

Q- What is the good method to quarantine tropical fish like guppies, molies, swordtail, corycats, tetra, gourami, angel fish, betta ect. Is salt method good if yes how much salt they can tolerate? Can you please describe the whole method. Other than salt what meds can be used for quarantine?

Q- When fish get affected with fungus do they scratch? Or is it just when they get parasites?

My goldfish was scratching and rubbing with their mouth and gills it looked. First I tried .3% salt (i.e. 3ts salt per gallon ) for 21 days not seen much improvement then tried fluke med but it didn't do much better either so finally tried antibiotics for fungus/columnaries and it worked. What do you think about it?