There isn't any chance a fish died (while hiding) after moving it to the new tank (I'm thinking loach)? A dead fish will increase ammonia levels very fast - by tomorrow it could be double that amount if the dead fish hasn't been removed. I can't think of any other explanation. Any leftover vinegar solution would have lowered your PH so I can only think of a dead fish causing that level of ammonia. Another possibility is that your tap water has Ammonia in it. I recently checked my city's water annual report and there was a significant amount of Ammonia listed in our drinking water! You can go to your City website and search for the water department and their Annual report - it will show you all the chemicals in your tap water as well as the average PH, the average Hardness and average Alkalinity. There may be some clues there. In the meantime some water conditioners (such as prime) will deactivate Ammonia and Nitrite levels for almost 48 hours. Now any test strip or other type of testing you may use will still show the ammonia and nitrites are still THERE - because they are still there - just in a deactivated form.
I still stand by my advise to not bother to clean a new tank with any chemicals, just wipe it down with damp paper towels. Now obviously if you see a lot of dirt on those paper towels you'll want to rinse the tank out with warm water and dry it well and wipe it down again, You mentioned using a vinegar solution and a couple more people are still using vinegar when it is USELESS - in fact it just makes the tank more of a danger. Bleach is used when you suspect some type of disease was present that killed fish in the past (because it kills everything) I would also use a very dilute bleach solution on a used tank since you don't know what kink of bacteria you may have. I don't know why people are so scared of bleach - ammonia isn't much better smelling and can cause a rash or an asthma attack just like bleach In your case, with the new tank - all you had to fear is dust and by wiping it out with a damp paper towel is good enough to get rid of the dust in the new tank. I'm not aware of any dangerous components used during manufacturing a tank that would require rinsing with vinegar or bleach - just get rid of the dust. The same goes if you find the spot when the old tank leaked - after it's repaired, wipe it out with a damp cloth - no chemicals are necessary.
