Immediate Nitrite spike in new 20 gal tank

Question
Because of bad advice from Petco, we filled a 20 gal take, added Cycle, salt, and a declorinator, then 24 hours later (after perfect testing) added 6 Cherry Barbs. Two died within 24 hours then the others have been OK. The levels are:

Ammonia: <.25 ppm
Nitrite: <1.0 ppm
Nitrate: 40 ppm

The remaining 4 fish seem to be showing no bad symptoms at all. I was doing daily water changes, but stopped because I wanted to allow the bacteria to form. I have added several doses of Cycle, and this is day 9. The levels are not rising, and with the addition of a single live floating plane the nitrate level is slowly decreasing. Should I return to daily 10% changes? Should I just let it ride? I took 4 gal of water from an established 10 gal tank when I first filled it, and on 11/21 I took a few tablespoons of gravel from the established tank and placed it in a screen and put it in the new talk's filter. Is there anything else I can do? Happy Thanksgiving.

Ralph Longo


Answer
Ralph,
you can simply wait, or you can add some more plants to assist.
However plants add to the bio load as well so make sure they are not dying or they will compound the problem.
You might want to start with something really easy like duckweed or azola would be even better.
For now, I would wait it out, check your levels every couple of days and you should be fine.
Further questions? Just ask.