He actually pulled a board out of a scrapped Toledo industrial scale. It had an RS232 interface. But I see no reason you couldn’t use an HX711. It has the i2c interface and there are imp libraries for that.
Your situation with loose tanks and possible load cell damage might be an expensive way to measure. If you had a large aluminum platform that all of the tanks sit on at the same time, you could weigh the whole thing. You would not know if one or more tanks were empty. One might be full, another empty.
Perhaps you will have to enforce some ‘administrative controls’. A specific cubby hole or a place for each tank that will control where it is weighed. If someone throws them around or doesn’t do it right, they can find another job.
This is really a tough one because it sounds like you don’t have much control over how other people handle the products.
Another “outside the box idea”. If the temperature of the liquid in the tanks is somewhat different than the ambient temp, you could put an IR camera inside the fridge and view it remotely. You will see the level in each tank by the line created from the temp on the outside of the tank where the liquid sits in the tank. Sort of a crude method, but just another idea. It would not matter where they put the tank as long as you can see it with the view of the camera.