My swordtail is all white spots, like tiny deposits on his body (not in his skin), and his tail fin is all tethered. How do I know it this is 'whitespot' and how do I treat it. None of my other fish are showing any signs of this.
if it is whitespot it will be like the fish is covered in salt, the whitespot is the size of a grain of salt.
If it is whitespot, which it sounds like, go to your lfs and get anti whitespot treatment, i use tetra contraspot although it depends what you can get. do a 20% waterchange before you treat the tank and also turn the heater up to 28 degrees.
it can be brought on by any number of things one of the main ones being stress, yes it is contagious through the water so the other fish are at risk, if you can't get to lfs soon turn the water up to 28 as this speeds up the lifecycle of the whitespot.
the fish might be ok until wed/thurs although the sooner treated the better, if the whitespot gets to the gills then there is no saving the fish. yes i would do another water change before treating as this gets rid of some of the spores, also when finished treating do a gravelvac to pick up any spores that have fallen onto the gravel.