one way to tell if it is ich or sand is look at it with just actinic lighting on. If it is ich it will fluoresce white a bit, if it's sand it just looks like sand.
I have this scare every so often and that is one way I found to tell easily.
Hyposalinity treatment is the safest proven method of treating ich, but it will also kill any other crustaceans and coral.
While many attribute success to garlic, there is no science that supports it, but that is not say it can't help.
Ich isn't always present in OUR tanks, but you can be pretty certain it is in any lfs
or suppliers systems, so any new fish should be quarantined if possible.
one thing you can do is to do small water changes daily using a gravel vac vacuuming up from the sand bed each time. The cysts you see on the fish are actually the end stage of their life cycle. When they disappear it is because the cyst has ruptured releasing thousands of trophonts (larval ich) into the system. Then they settle in the substrate for about 10 days, then on to a free swimming stage, the only stage of the life cycle when they are susceptible to treatment, until they attach to a fish and begin the cycle all over again.
By regularly vaccing the sand, you remove some of the trophonts.
Flashing/scraping the gill plates and rapid, labored breathing are the first symptoms as the ich gets trapped/attached in the gill tissue and it is much easier than attaching to the body or fins.
What else is in the tank?
is the gramma the only fish?