Dumbest and very first thing I ever did....oh man...luckily It turned out to be an accidental treatment procedure.
My first purchase in the hobby was from a pet store that sold saltwater, not specialized in. They gave me gravel, a hang on filter, a fluorescent light, salt, a 10g, and a bubbling volcano, tap water conditioner...and a snowflake eel and a pajama cardinal...no instructions. See where this is going?
My 2 day process of ugh
Step 1: set the tank on the stand
Step 2: assemble accessories, light, filter, add gravel, etc
Step 3: put the fish in the tank, using their water
Step 4: fill the aquarium with tap water
Step 5: add the salt
Step 6: wait, what?
Step 7: Google the heck out of this hobby
Step 8: get stuck wasting brain power at another forum, and another, and another...
Step 9: found R2R
Step 10: went back to complain to the pet store and buy what i really needed.
Ok so it seems this was not as dangerous as I first assumed. In a way it was like I just gave the fish a freshwater dip, though mixing salt in their water had to be displeasing. These two fish lived longer than any other fish in my learning curve and are currently living in someone else's tank now! The gravel turned out to be silica based and made diatoms. The hang on filter was ok, but needed changed regularly. The bubbling volcano was the worst part about it. It was essentially a protein skimmer action chamber with no collection cup! Constantly blasting micro bubbles to the surface led to massive salt build up and stinky over spill. Oh and the light was designed for fish only freshwater and had no photosynthetic capabilities.
Lesson learned:
DO NOT BUY ANYTHING WITHOUT CONSULTING SUCCESSFUL HOBBYISTS FIRST! YOU WILL REGRET IT!