When I first got into 70mm I desperately searched for a tank, every now and then a 70mm tank would show up on eBay and sell for $350-$450... Insane prices...
So I contacted a specialty company that made me a stainless steel 70mm reel (holds 15 feet / 5 meters of film).
Then made my own daylight tank... This is only good for B&W processing, because, don't laugh, part of it is WAX, so you can't heat it up to C-41/E-6 temps (you can I suppose but I wouldn't try it).
Anyway I developed many rolls on it, it is not fully daylight tight, I once developed near the noon sun window, light went right down the center and added some flare to the images on the edge of the reel, but so long as you don't have a glaring light above your head, you're fine, just use a dim light while processing.
It takes exactly the same amount of chemistry to process/cover the film as the $350-$450 ones, and that amount is 2L per 15 feet of film
The daylight tank part only cost me labor and $30 to make. So it's FREE.
But the reel is at cost $100 + $16 shipping CONUS.
Anyway I finally got an official one made by a factory and have held onto this as a backup but I don't need it.
First to buy it wins.
PS I'm also selling some 70mm film in another post.