The presence of small, (.5 to 1.0 mm) white dots (kind of like salt) scattered about on the fishes' skin. Sometimes bobbing up and down with their head above the service again trying to get extra oxygen as ich infestations often start in the gills and this robs the fish of the ability to properly respirate. Fins are often held down and are clamped as well. As the he infestation progresses, the fish become more listless, loose color, and often develop secondary fungal and/or bacterial infections.
The parasite forms a nodule under the skin or gill of the fish host. It constantly turns and moves under the skin, feeding on destroyed cells and body fluids. It continues to feed on the cells until it matures, causing damage to the skin tissue.
so that description is the best way I can bring across to you what ich is
as for a chemical test? only observation of the fish will you know