Here is a link to what a grain mite looks like:Grain Mite
Here is an article about mites and tank pests: Tank Pests
And a more thorough one with links to pictures of the insects themselves: Bug guide
I did notice in the section on Grain or Mold mites that it mentions a sweet/minty odor. How do you smell this over the EE and tank smell? I am not doubting, I am curious. Wondering if there is a way I can smell it too in my tank.

I also noticed mites in my tank again today. I had them last year around March or April.
I noticed them around the food dish in the iso tank with EE substrate, so looked hard in my main tank and didn't see any movement. Unfortunately my sand is the exact same size and color as the grain mite.
When removing the food (I leave it in for 2-3 days sometimes, depending on whats in the dish) I noticed one piece of food that looked to be covered in sand, but on closer inspection, what looked like sand settling, was actually mites moving all over! It STILL looked just like my sand, but kept on moving. I totally creeped out!
So I've ordered some predatory mites and those should be here within a few days. My tank is just too big to be doing all the cleaning necessary, as I really don't have the time what with work and family.
So in preparation I've put a thick vaseline line around the top edges of my main tank and iso tank to prevent any mites from possibly escaping. I was hoping to do a deep clean soon, but will have to wait now until the mites have done their business, which can take quite a few weeks.
Back to you Salt and Pepper: Please note that the info on ridding your tank of mites on the page I linked is very limited. It is actually necessary to bathe your crabs again a week later, replacing the substrate again and boiling all tank ornaments. It's a good idea to keep wood and things out during that week, use only plastic hideys (I used a plastic flower pot with a doorway cut in it, upside down for their hidey) and ornaments that are easy to clean.
When bathing your crabs to rid them of mites, make sure the water is tepid - as in lukewarm, not room temperature. Room temperature is actually rather cool and will shock the hermies. It should feel neither warm nor cold on the inside of your wrist when you put your wrist to the water.
Put them in upside down, forcing them to come out of their shell to right themselves, which forces water into the shell helping to flush it out. Have them do this twice to be sure. You have no idea if there are any mites hiding inside the shell.
Place them back into a tank with fresh, clean substrate and sterilized tank decor and extra shells. Feed carefully, removing food daily.
I think where mites are concerned, you don't want to leave food too long to encourage more mites, allowing more eggs to hatch that may have been laid in the food itself.
So to trim it down, completely change substrate, sterilize the decor and shells, wipe down the inside thoroughly with vinegar water, bathe the crabs to remove any mites that may be hiding on them or in their shells, repeat a week later. You may want to even repeat again another week later just to be sure. Be diligent about changing out food regularly.
Hope that helps! I know I'm not leaving even dried food in their for long periods any more, except food that doesn't contain grains.
