Hi guys, I am an active hobbiest with Saltwater fish and can easily, for the most part, take care of them without much difficulty. My question, however refers to Guppies with Freshwater or "brakish" water. The Wal-mart that I visit, unlike other Wal-mart stores, has an excellent success rate of fish, very rarely have I had fish bought from there that have died, or have even seen dead fish in their store. (Pet departement employee of the month)? Question: All the water in all of the fish stores, flows through all of the tanks, even tanks that have guppies in them. So would you suggest, that I add salt to my own tank at home, regardless that the water at Wal-mart flows through the same tanks? The sign under the tank recommends adding salt for guppies, but do you guys think they have added salt themselves, eventhough the water flows through all the tanks? Thanks to those of you who help!