Internal protizoans usually take a while longer than a couple of days to kill a fish. You will usually notice them not eating, and staying in a corner or towards the back of the tank, not having any interaction with other fish. This could be a water related problem, or a bacterial problem, especially with the patches on the angel.
Have your water tested, and have the lfs write down the numbers. Post those numbers here. Often when a shop says the water is fine it actually isn't, or they will try to sell you something to adjust your pH, which does much more harm than good.
If the ammonia & nitrite come out as anything other than zero it's a cycling problem, and we need to look into your water change procedure, water conditioners used, and filtration. If the ammo & nitrites are zero, with nitrates 40-50ppm or less it is probably bacterial. Being in the US there are many good antibiotics available, I would start with Maracyn & Maracyn II, and work from there.
You can med a fish in a tank that doesn't have a cycled filter IF you do 50% water changes daily. In a mature tank with gravel you can often rig a small bio filter for the med tank using the mature gravel, this thread shows how to make a cheap one, or you could just buy a small box filter, put in some mature gravel, and add a small air pump.
http
/www.fishforums.net/Super-simple-5-m...ter-t85297.html
