In setting up a new freshwater planted aquarium, I needed to know and track my water quality parameters closely to make sure everything is establishing correctly. I had a very old GH test from Aquarium Pharmaceuticals that no longer worked so I needed to replace it. I initially bought the Elos GH test kit thinking it would be a "win-win" -- new test kit that uses non-toxic reagents. But it didn't work. Frustrated, I asked other people in an online aquarium forum which GH test kit they used. They recommended the Nutrafin kit. And guess what? THIS KIT WORKS. Bonus: It's easy to distinguish the color change that this kit uses; that isn't the case with many GH test kits (I'm looking at you, AP!). Definitely worth the money spent, because I now have a handle on how often I need to change my tank's water, and how much of my GH additive to use each time. Save yourself time and money: if you need a GH test kit, get this one.