High Nitrites

I wouldn't worry about the salt...it really isn't necessary. Just wait it out test every so often as I mentioned above, and you should be on your way. You have done a lot of water changes to keep ammonia and nitrites low....I think you have a new tank bloom going on.
 
OK, so besides water changes, just wait it out? I can do that.

I do have a pleco. So, I shouldn't put any marine salt in for my swordtails? We were told by the LFS to add salt to help their immune systems?

Don't know where LFSes get these notions. Swordtails are a freshwater fish, end of story. Their relatives, the mollies, are sometimes found in brackish environments but not swordtails.
 
I found that if you do 50% water changes daily until the levels are within safe ranges then it should do fine, and balance quicker. I had my fish at levels that were off the chart for weeks when I added new substrate and after doing so many water changes the tank was cycled in two weeks.

I did add some bio chems but I think they did more harm than anything
 
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