Mesh Bag for raising substrate

I saw a youtuber adding lava rock to a nylon mesh bag and creating a raised "hill" area. He then poured his substrate over the rock bag. This way he did not have 8" deep substrate where he wanted the hill.
Do they make an actual bag for this, or can I use any nylon mesh bag with a draw string? When I add "aquarium" to me searches is only giving me filter media bags, which are way too small. But there are plenty of ditty bags, laundry bags and gym bags to choose from. Some of them are colored though. And I'm not sure if that would be a problem. Probably not, as I'm sure the nylon mesh is colored all the way though.

What do you think?

 

Would using tights (panty hose) not do the job?
If your substrate is black then just buy a black pair so it wouldn’t show under the substrate.

 

Would using tights (panty hose) not do the job?
If your substrate is black then just buy a black pair so it wouldn’t show under the substrate.

If they are aquarium safe I'm sure they would. They might be harder to work with though. Either way I'll have to buy something.

 

As long as they’re clean with no detergent residue they’re safe to use, many people use them in aquariums for a variety of purposes. I‘ve used them around a breeder box to stop cory fry escaping through the slits.

 

I'll bet the elasticity of a stocking would be great for putting around a breeder box.
Good tip.