Tropic Marin High Precision Hydrometer

Tropic Marin’s High Precision Hydrometer verifies accurate salinity readings, helping protect sensitive tank inhabitants from harmful water changes.

Ensure that your equipment is reading correctly and your aquarium is at the right salinity with Tropic Marin's High Precision Hydrometer. 

Many tank inhabitants are sensitive even to minor changes of the water conditions. Unfortunately as we've all experienced, salinity reading equipment as well as calibration solutions can drift over time and it can occasionally be a challenge to ensure equipment is always calibrated correctly. That's where the Tropic Marin Hydrometer comes in. The Tropic Marin High Precision Hydrometer provides an exact and reliable measurement of specific gravity, and it never needs to be re-calibrated, so it's a perfect reference device for calibrating other equipment.

• High precision hydrometer for determining the specific gravity in aquariums.
• Maximum deviation: 0.001 at 77° F (25° C).
• Scale from 1.021 to 1.031.
• Resolution: 0.0001.
• Handmade.

The hydrometer is handmade and designed to float vertically in the water. The maximum deviation is about 0.001 at 77° F (25° C).

Please note: The salt content of sea water is usually measured as specific gravity. Please check for the blue printing and the indication “Specific Gravity” at the Tropic Marin High Precision Hydrometer.

What's Included?

• Tropic Marin High Precision Hydrometer.

How to Use

Temperature first. Specific gravity is temperature dependent — as temperature rises, specific gravity falls. The sample must be at 25 °C / 77 °F for the reading to be correct. This is the single most common reason two devices disagree.

Tropic Marin's method:

1. Fill a measuring cylinder with a maximum of 400 ml of aquarium water at 25 °C / 77 °F.
2. Make sure the hydrometer is dry and clean.
3. Place it gently into the water and let it float freely — it must not touch the sides or the bottom.
4. Read the specific gravity off the blue part of the scale, at the level of the water surface — not at the level of the meniscus, which creeps higher at the edges. Reading the meniscus is the other common error.
5. Afterwards, rinse the cylinder well with fresh tap or RO water to remove salt residues, so they do not distort the next measurement.

What you should be reading. Natural seawater at 35 ‰ (psu) is 1.026 at 25 °C / 77 °F. Tropic Marin's recommendation for aquarium water at 25 °C is 1.025 to 1.027, depending on the tank type — which is exactly the span marked in blue on the scale.

Do not confuse it with the density version. Tropic Marin also make an Aräometer for the German-speaking market, which has a green scale marked “Dichte/density”. This one is the specific gravity instrument: check for the blue printing and the words “Specific Gravity”.

Handle it as glass. It is mouth-blown glass with a weighted bulb. Lower it in, never drop it.

Tests per Kit

Unlimited — there is nothing to consume. This is an instrument, not a reagent kit. No chemicals, no refills, no expiry, and Tropic Marin state it never needs re-calibrating, which is what makes it a useful reference against which to check a refractometer or a swing-arm.

Specification:

• Scale: 1.021 to 1.031
• Resolution: 0.0001
• Maximum deviation: 0.001 at 25 °C / 77 °F
• Recommended aquarium range marked in blue: 1.025 to 1.027
• Mouth-blown glass. Made in the EU.

What is in this pack, and what is not. This is Tropic Marin article number 51002 — the hydrometer on its own. The measuring cylinder is a separate article (51000), and Tropic Marin also sell the two together as 51022.

You will need a vessel the hydrometer can float freely in without touching the sides or bottom. Tropic Marin's own cylinder is 36 cm / 14 inches tall and holds 500 ml, and their method fills it with no more than 400 ml — that is the depth and clearance the instrument is designed around. A narrow drinking glass will not do.

Freshness & Storage

Every batch we dispatch carries a minimum of 6 months' remaining shelf life. Store this product in a cool, dry place away from direct sunlight, with the cap or inner foil closed tightly after each use.

Backorder & Dispatch Timeline

This item is stocked to order. Back-orders are consolidated and placed with our overseas suppliers once a month, on the last day of the month, and all such orders are shipped before the 15th of the following month.

Back-orders cannot be cancelled once they have been placed with the supplier. If you cancel before that, payment-gateway charges of 2% plus GST are deducted and the balance refunded. In the rare case a supplier cannot fulfil the item, we will offer you an alternative first, and refund in full with no deduction if you would rather not take it.

Returns & Replacement

Returns are accepted within 7 days of delivery, provided the item is unused and in its original packaging. Manufacturer-sealed items cannot be returned once the seal is broken, and sale-priced items are not refundable.

If your item arrives defective or damaged, message us on WhatsApp with your order number — or email us, if you would rather — and we will replace it. Approved replacements are delivered within 3 to 5 business days. Transit damage is covered by insurance on every shipment. If tracking shows delivered but nothing reached you, tell us within 72 hours, which is the reporting window Indian couriers allow. Damage caused during installation or use is not covered; replacement spares for such cases are chargeable.

Full terms are on our Cancellation & Returns page.