I've read through this thread, and will respond by backing up a bit. It is dangerous to jump in with too many "cures" at once. So this will go from step one, no offense to anyone. Ich
: Raise the temp to 85F, or even higher if fish can tolerate it. Angels and cardinals can, so close to 90F for at least a week [the Danio would not manage however]. No medications are needed if you get it to 90F. I have fish that can't handle this, so I go to 85F and use Coppersafe (made by Mardel). One treatment. Do a good water change (50%) first, add the CS and raise the temp by adjusting the heater so it will be gradual [you can warm it by 4-5 F degrees with the water change first]. Discontinue plant ferts if any are normally used. Leave it for a full week. Turn the heat down to normal after 7 days and let the tank temp naturally lower. Do a partial water change 3-4 days after that. End of ich. If you need to do water changes during this period, it will dilute the CS. Adding half the amount only for replacement water works. I have some very sensitive wild-caught fish, and this treatment has never harmed them. Ammonia
: Remember that using Prime will detoxify the ammonia by changing it to ammonium which is harmless, but tests will still show ammonium as "ammonia." Prime is effective for 36 hours, maybe 48 max. Normally, if ammonia is in the tap water, using Prime (or another conditioner that detoxifies ammonia) with a water change will deal with the initial influx of ammonia, and by the end of its effectiveness the live plants and/or bacteria will catch up. This is the only safe way to deal with ammonia in the source water. Cardinal Tetra
: This is a highly sensitive species; the Coppersafe is the only medication I have ever used and not lost cardinals. Also, they are not a fish for "new" tanks. Whenever I have added cardinals to a tank that is less than 5-6 weeks established [and I don't mean cycled, I mean fully cycled and then established which with sufficient live plants will be in 5-6 weeks] I have either lost them outright or they came down with ich.
This also makes them highly sensitive to pH and chemicals. Cardinals occur in water so soft the hardness is practically unmeasurable, and the pH is less than 5, often around 4. Hard water causes severe stress, and calcium blockage of the kidneys among other things. In post 1 it was mentioned that pH is very high, with no number, but as you get it down to 7 with chemicals I will assume it is maybe 8 or more? This will kill cardinals within months, maybe a year or two at best. And the pH adjusting stuff will add stress and weaken them. Very probably a major contributor to the ich. pH in general:
Adjusting pH should never be attempted until you know the hardness and deal with that. Rather than repeat, I'll refer you to my article that covers this relationship and mentions how to lower hardness/pH safely if that is needed: http://www.tropicalfishkeeping.com/f...quarium-73276/