JBL hydrometer
Hydrometer for saltwater aquariums

  • Precision glass spindle and measuring vessel for measuring the salt content (density) in marine water aquariums
  • Convenient to use: half fill the measuring vessel with saltwater, insert the clean hydrometer, read off values after 1 minute.
  • Reading accuracy of 0.0005 units and therefore also suitable for scientific purposes. Reading range of density from 1.016-1.028 (recommended range: 1.021-1.025)
  • Thermometer and built-in temperature correction scale from 9 to 32 °C. Transport cylinder (height 33.5 cm) serves as measuring vessel
  • Package contents: 1 hydrometer for marine water with built-in thermometer + measuring vessel with stable stand
Find out more
Price: 41,40 €
Recommended retail price incl. VAT
You can find this item in your specialist and online shop
Product information

Nature at Home – Home for Fish and Plants
Lesser animals and corals need to feel as much at home in the aquarium as they do in the wild. In a marine water aquarium, this includes the right water values, the right light, a varied and species-appropriate diet and of course the right salinity.

Density in marine water aquariums
When aquarium water evaporates, salts remain and they increase the density in the aquarium. To prevent damage to fish and invertebrates it is important to check the density regularly and to take any appropriate steps.

Density is temperature dependent:
At 25 °C, hydrometers indicate exactly the right density. Higher temperatures will require a correction factor, which is indicated in the JBL hydrometer on a scale next to the built-in thermometer. At 30 °C, for example, 0.001 needs to be added to the indicated density of, say, 1.022. The correct density at 30 °C would therefore be 1.023. At water temperatures below 25 °C a correction factor would have to be subtracted, e.g. at 20 °C 0.001 would have to be subtracted from the displayed density value. So if this is 1.025, the real density at 20 °C is 1.025 minus 0.001 = 1.024. If the water temperature in cold marine water aquariums is 15 °C, a correction of -2.5 ° needs to be made.


JBL hydrometer

Art. no.:
EAN Code:
24,5 cm
Volume packaging:
1.84 l
Gross weight:
180 g
Net weight:
120 g
Weight factor:
Packaging dimensions (l/h/w):
75/390/70 mm


Animal species: Corals, Gobies, Mussels
Animal size: For all animal sizes
Animal age group: All aquarium fish
Volume habitat: For all aquariums
Material: glass / metal (aluminium)
Colour: white / transparent / green / red

Electronic label / illuminant

Mercury: No
Dimmable: No
The hydrometer is broken. It contains a red liquid. What does the red liquid consist of and is it toxic?

The hydrometer doesn’t contain any mercury. The liquid contains an alcohol solution with colouring. It is non-toxic. Both ingredients are quickly broken down by the bacteria in the aquarium. Furthermore the diluting effect should be taken into consideration. The silvery pearls are an iron compound and are therefore harmless. Simply siphon them out of the aquarium.

What range does the scale of the hydrometer cover?

A reading accuracy of 0.0005 units makes the hydrometer very accurate.
The built-in thermometer, which covers a scale from 9°C to 32°C, and the temperature correction scale gives you the highest precision. The density is determined in a range of 1016 to 1028.

Blog (opinions & experiences)

JBL TV #43: All the important values in seawater - Testing saltwater reliably

This is how to be sure you’re checking the water values in your marine aquarium simply and safely.

Find out more

Display Accuracy vs. Measuring Accuracy - Different Results When Measuring Temperatures

You may find the differences that can arise when measuring the temperature with different measuring instruments and methods, confusing. Most people tend to trust a digital device more than an analog device. Is this justified?

Find out more

Inaccurate water tests – or did I do something wrong after all?

In the aquarium scene we often hear people talking about “accurate” and “inaccurate” tests. But mostly they mean a rougher or finer scaling of the output values.

Find out more

Keeping an eye on the most important water values

Professional water analysis sounds very expensive. But the professional water testing in your aquarium or pond at home also works on a high level and above all it is simple and inexpensive.

Find out more
Laboratories and calculators

Water Analysis Online Laboratory

Enter your water parameters and get an in-depth analysis of your values in a matter of seconds. You enter your water values – and we analyse! Here you have the opportunity to enter the measured water values directly into the JBL Online Laboratory. This will analyse your values and explain and submit corrective measures.
Reference guide (Themeworld)

Marine water

There is a solution to almost every problem! And the hardest part is finding the cause of the problem.

Deficiency symptoms

Here’s how to prevent deficiency symptoms in fish and plants

Marine water treatment

What maintenance does your marine aquarium need?

Daily care

How much daily or weekly care is involved? What are the basic maintenance measures for your aquarium?

Marine water - the water

What exactly is marine water? What is so special about marine water? How to create perfect marine water?

Installation technical items

How and where in the aquarium do you fix and install technical items? Tips and tricks for the installation of all technical aquarium products

Marine water - technical items

What is the difference between a marine and a freshwater aquarium? What is especially needed for a marine aquarium?

Heating and cooling

Why is 25 °C ideal? This is how to heat or cool aquarium water

The marine aquarium

Holiday at the coral reef - in your own living room! Marine aquariums are the most exciting branch of aquatics


safety instructions

  • safety instruction for accessories
    • Filename:
Customer reviews


Overall rating: 5.0
3 public review(s) for this product.

0 Reviews

3 more reviews in other languages

3 Reviews in other languages

Z. Khawaja - German


Z. Khawaja - German

Macht was es soll.

Einfach zu benutzen und genaue werte.

bennys riff welt - German

Richtig schön der Zylinder ist auch super der da bei ist

die Zahlen sind auch sehr gut ablesbar. bin Echt Begeistert

A word about cookies before we continue

The JBL Homepage also uses several types of cookies to provide you with full functionality and many services: We require technical and functional cookies to ensure that everything works when you visit this website. We also use cookies for marketing purposes. This ensures that we recognise you when you visit our extensive site again, that we can measure the success of our campaigns and that the personalisation cookies allow us to address you individually and directly, adapted to your needs - even outside our website. You can determine at any time - even at a later date - which cookies you allow and which you do not allow (more on this under "Change settings").

The JBL website uses several types of cookies to provide you with full functionality and many services: Technical and functional cookies are absolutely necessary so that everything works when you visit this website. In addition, we use cookies for marketing purposes. You can determine at any time - even at a later date - which cookies you allow and which you do not (more on this under "Change settings").

Our data protection declaration tells you how we process personal data and what purposes we use the data processing for. tells you how we process personal data and what purposes we use the data processing for. Please confirm the use of all cookies by clicking "Accept" - and you're on your way.

Are you over 16 years old? Then confirm the use of all cookies with "Noticed" and you are ready to go.

Choose your cookie settings

Technical and functional cookies, so that everything works when you visit our website.
Marketing cookies, so that we recognize you on our pages and can measure the success of our campaigns.
I accept the YouTube Terms of Service and confirm that I have read and understood the YouTube Terms of Service .

PUSH messages from JBL

What are PUSH messages? As part of the W3C standard, web notifications define an API for end-user notifications that are sent to the user's desktop and/or mobile devices via the browser. Notifications appear on the end devices as they are familiar to the end user from apps installed on the device (e.g. emails). Notifications appear on the end user’s device, just like an app (e.g. for emails) installed on the device.

These notifications enable a website operator to contact its users whenever they have a browser open - it doesn’t matter whether the user is currently visiting the website or not.

To be able to send web push notifications, all you need is a website with a web push code installed. This allows brands without apps to take advantage of many of the benefits of push notifications (personalised real-time communications at just the right moment).

Web notifications are part of the W3C standard and define an API for end user notifications. A notification makes it possible to inform the user about an event, such as a new blog post, outside the context of a website.

JBL GmbH & Co. KG provides this service free of charge, and it is easy to activate or deactivate.