due to a house remodel I had to move 6 fish from a 29 gallon to a 10 gallon for 2 months..no problem...I set 29 back up..all fine..3 weeks later I added 7 new fish along with a petstore advise to add aquarium salt...now a week later I have lost 11 fish...1tsp to 5 gallons is what I was told....I have done a 40% water change 3 days ago and fish are still dying..PH is fine ..............HELP!!!!!

What kind of fish? What about ammonia and nitrate levels?

Are the scales sticking out like a porcupin? If so it could be Dropsy? That is bad and very fatal to fish.

Any unusual behavior? color, panting, bloat, anything?

Could be Ich, But I doubt it. I would guess either a Bacteria or Fungal issue. You can treat with Primafix and Melafix and that will cover both. Sounds like your time is of essence, so do both at the same time. Follow the instructions and remove all carbon from filters. Raise temp to 82 to 84 degrees slowly, 1 or 2 degrees every 4 hours. Add I tsp salt per 10 gallons and after 50% water changes (Only add salt to equal amount of fresh water added) every other day prior to treating water.

I doubt they would be able to tell from a water sample. As for the salt, the dose sounds a bit strong but I don't think was the cause. My guess would be the fish you got from the LFS. Why using a guarentine tank for a few weeks is a good idea. Also anything you have used in that tank soak in Bleach water overnight to kill it. Otherwise you can reinfect your tanks again. This is buckets, nets, scrubbers.....Anything.