That is why I was suggesting to make adapter sleeves to securely hold a variety of known brand test vials to eliminate the need to worry about pouring test solutions back and forth and reducing the risk of a vial getting knocked over. The 3d printed version that
@melev was originally referencing would be the best candidate for this; especially if he can get with the guy printing these and modify the design of the stir plate to accommodate bushings for various tests kits. There are numerous product on the market that can accomplish the same goal, but I would personally buy one that is made to work with my redsea test kits, etc- rather than fumbling with other vials and extra steps/precautions that would make the test more difficult to complete than without the stir plate.