Rheoscopic fluid is what that stuff is called
This stuff is non-toxic, does not react with anything will not stain, comes in many colors, Can be pumped, or will flow with heat (we all have lots of that available!) and is reasonably cheap!
A 100 Rheoscopic Fluid, 16 oz . . . . . . . . $6.95
A 105 Rheoscopic Fluid, 32 oz . . . . . . . . $11.95
A 110 Rheoscopic Fluid, gallon . . . . . . . $36.95
I would not use it in a WC system directly, apparently it will grow some things. Also, since it is made with
microscopic Mica, I really doubt it will cool components very well, and might clog things if your block is a little scummy inside.
Edit: Another thing: If your pump operates at a high volume, I really doubt if you would see anything swirling or whatever.