While using popular aquarium test tubes we noted with disappointment, that when shaking to mix test solutions with the water sample, drops of the corrosive mixture ended up on our fingers and the floor. This led us to source leak-proof caps, so that keeping our aquarium water in check does not mean exposing our skin to highly toxic chemical solutions nor having it splash the bench-top and floor. Note: As the neck of the test tubes - given the screw-on caps - are narrower than the alternative, it may be helpful to use a nozzled 5ml syringe for dispensing aquarium water into the test tubes.