White Spots Ich Or Not?

[tangohotel]

My tank is 260litres and has Angel fish, various tetras and swordtails. About 10 days ago white spots appeared on about 3 of the swordtails, nothing else. As far as I know the temp has remained a constant 28C and the water tested negative for nitrates, ammonia etc I have treated for ich, but the spots remain - no worse and no better and not spreading. I now wonder if it is ich, as the spots are not on the fins but sort of along the top of the back of the fish, they do not look poorly in any way and are eating and swimming normally. Any suggestions?

 

[zigzagabout]

You have to treat more than once and also do a complete hoover of gravel every other day for a good couple of weeks to clear the white spot desease. It is strange that no other fish are showing any signs though, do the spot look like grains of salt? Perhaps post a photo, as this might help.

 

[tangohotel]

I have tried to upload a photo but it says it is too big. Some of the spots are bigger than grains of salt and concentrated on the back. I have kept fish for many years and seen and treated ich before, this doesn't look like classic ich as the fish are not covered all over.