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Hydrometers and Refractometers

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Help and advice on shopping for: Hydrometers and Refractometers

Specifically designed for saltwater aquariums

Aquatic species survive at varying salinity levels, so measuring salinity or the dissolved salt content of water is crucial. The health of your marine tank might be harmed by too much or too little salt in the water. Find top brands such as Fluval, D&D and Hanna here at Swell UK.

What are hydrometers, refractometers, and salinity test kits?

Hydrometers, refractometers, and salinity testers let you measure the salinity or specific gravity of the salt water in your marine aquarium or in new salt water you're preparing during water changes. Measuring salinity or specific gravity is vital to ensuring the health of fish or inverts in marine tanks.

Why might I buy salinity test kits?

Salinity levels or specific gravity levels are essential for both freshwater and of course saltwater tanks. Too much or too little salt in your water can mean that the life you are keeping in your tank can suffer, and balancing it can be a difficult act considering the number of water changes you need to do over the months and years you keep your tank. As water evaporates it causes the salinity and specific gravity to increase, so you need to check regularly to ensure the water isn't becoming too salty.

What are the main types of salinity test kits?

There are three main types: refractometers, hydrometers, and salinity testers. Hydrometers are the most commonly used and measure the specific gravity or density of the water. They're cheap and easy to use, but not as accurate as either refractometers or salinity testers. Both refractometers and salinity testers tell you how much salt is present, and they're less susceptible to dodgy readings caused by water temperature, which will affect all hydrometers.

What features should I look out for?

Our hydrometers and refractometers all provide an accurate and convenient method of measuring specific gravity and salt levels in marine aquariums. Compact and easy to use, they can be permanently installed inside the tank for continuous readings thanks to their strong suction cup. The slim, low-profile design of the Fluval Sea Hydrometer camouflages well inside the tank and will not diminish the aesthetics of the aquarium. It can also be used as a portable device, allowing you to take samples simply by submerging them in the water.