Can Guppies thrive in salt water?

That's the thing... it's aquarium salt... not marine salt. If it were marine salt, I would definately need to do a step down type acclimation. I've heard of people that get done treating ich, and remove the aquarium salt as quickly as possible... until I get further guidance, I am taking what I believe to be the safest course. Since I do not know the concentration of salt that the previous owner used, but I do know that she thought it was marine salt, I am going to assume that she followed the directions. This puts the dose at 1 rounded tbsn per 5 gal. Since my bucket is 2.5 gal, I am adding 1/2 flat tbsn per bucket (slightly less than directions) and dripping. After it's full, I will go a little less with every water change, until I am adding unsalted water. If anyone sees a problem with this, or believes it completely uneccessary, please let me know.
 
Guppies can withstand salinity 150% greater than what is in the oceans. This means marine salt - not table salt, not aquarium salt, not kosher salt.

You cannot drop them in and expect them to survive but must be acclimated slowly - a peroid of several weeks.
 
AquariaCentral.com