Fluval Sea Hydrometer for Aquarium, Medium
$ 2.41
Don’t listen to the people that say it goes high in tap water. It does, but that’s because that’s not how it’s meant to be used. Get it in your tank and get all of the bubbles out and it works great. Mine was getting towards the top of the green area so I topped of my tank with RODI water and I could watch the gauge go down as the salinity went down. Great accessory to have in my tank.
