what do you mean by tanks

Just like when I embroidered on a T-shirt, after washing (even sitting for a while) the marks came out....You are talking indentations from the hoop, correct? Welcome to our Cute family and *4U

OK we call them tanktop You can use sticky stabilizer. That's what I use for them and t-shirts
*4U

The hoop marks should relax and disappear after it has been out of the hoop for a bit, and almost definitely upon washing, but if you want to avoid them altogether (for instance if the shirts are for gifts or for sale) then yes, you can use sticky stabilizer. Or you can use cut-away stabilizer and use spray adhesive to stick the tank to it, or use a fabric glue stick for the same purpose, or you can even just pin your tank to the cut-away stabilizer (just be sure to watch and make sure you don't try to stitch over a pin!). Whichever you decide to do, be very careful that you don't stretch the fabric while stabilizing it. That will lead to puckers and other undesirable effects when you are finished. The stretchiness of the fabric is also why I wouldn't recommend a tear-away stabilizer, in case you were wondering. Tear-away just doesn't tend to be strong enough to produce a good result on stretchy fabrics. Good luck and have fun with your project!

Good answer cutiepie, you can't go wrong with that advice tatorbugcreations, welcome to our *Cute* family, hugs and a flower for you sweetie.