What is Ich? How do I know if my fish has it?

ich another way of saying white spot its a parasite that attaches its self to a fish to host it & appears on the fish as tiny white pin headed spots are with marine fish the spots can be a little larger around 5mm your fish will show other sign that can relate to white spot (ich) & that is flicking rubbing against rocks sand etc also they may gasp near the surface of the water....

velvet is another parasite that can show the same sign`s as white spot (ich) but it`s less common & the spots are more gray more like dust