What has always worked best for me is Hikari ich-x or Kordon rid ich plus. You need to use a full dose for 7 days, turn up the heat to 87 or 88. And vacuum the substrate with a water change every other day. I fought ich for a month once, then I used those products (they're the same ingredients, so doesn't matter which one you use) and did that other stuff and it cleared up in a few days. 7 days to make sure it's gone. The tetras will die tho, so put them in something else where they can get a half dose.