7 recommended hydrometers! Accurate maintenance and management of breeding water for saltwater fish!

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What is a hydrometer

A hydrometer used in an aquarium is an instrument primarily used to measure the density (concentration of salt, etc.) of seawater. Marine organisms such as saltwater fish have a comfortable specific gravity, and specific gravity is extremely important when breeding saltwater fish.


If you do not create breeding seawater with the optimum specific gravity, diseases may spread, or in the worst case scenario, the fish may die. A hydrometer is an essential tool for marine aquarists in order to keep saltwater fish healthy.

Types of hydrometers and how to use them

There are three main types of hydrometers. Let's take a look at the characteristics of the three types and how to use them.

pointer type hydrometer

This type of hydrometer puts seawater inside the hydrometer and reads the value indicated by the needle. The advantage is that it is extremely easy to measure, as it can be measured by simply scooping up the seawater in the aquarium. There are also products that can be attached to the wall of the aquarium to constantly check the specific gravity.

Baume hydrometer

This is a type of hydrometer that floats in seawater and reads the memory on the surface of the water. Like the pointer type, it is characterized by being very easy to measure. It is also useful when making artificial seawater.


This is a type of hydrometer that checks the specific gravity by taking a small amount of seawater and measuring the refractive index of the seawater by passing light through it. Compared to the pointer type and Baume type, it is less convenient but is said to be more accurate.

7 Recommended Seawater Hydrometers

We have put together a list of recommended hydrometers. Find a hydrometer that is easy for you to use.

tetra hydrometer

Kamihata Deep Six
orca hydrometer

Kamihata compact seawater hydrometer PETIT METER

Instant Ocean Sea Test

Nisso AQ-29 Seawater Hydrometer

GEX Hydrometer ATC Seawater Concentration Refractometer

Let's maintain proper seawater with a hydrometer

When breeding saltwater fish, the management of breeding water is more severe than for freshwater fish. Unlike freshwater fish, their specific gravity changes quickly due to evaporation of seawater and water changes in the summer.

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A small change in specific gravity can cause your pet to become unwell and become sick, so be sure to manage your breeding water on a daily basis. Find a hydrometer that suits you and take good care of your saltwater fish so they can live a long life!


A hydrometer is essential for breeding saltwater fish