---
product_id: 6541540
title: "Fluval Sea Hydrometer for Aquarium, Medium"
brand: "hagen"
price: "£17.61"
currency: GBP
in_stock: true
reviews_count: 13
url: https://www.desertcart.co.uk/products/6541540-fluval-sea-hydrometer-for-aquarium-medium
store_origin: GB
region: United Kingdom
---

# Compact, low-profile design Large, easy-to-read markings Accurate specific gravity measurement Fluval Sea Hydrometer for Aquarium, Medium

**Brand:** hagen
**Price:** £17.61
**Availability:** ✅ In Stock

## Summary

> 🌊 Stay salty, stay savvy — master your marine world with Fluval Sea Hydrometer!

## Quick Answers

- **What is this?** Fluval Sea Hydrometer for Aquarium, Medium by hagen
- **How much does it cost?** £17.61 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.co.uk](https://www.desertcart.co.uk/products/6541540-fluval-sea-hydrometer-for-aquarium-medium)

## Best For

- hagen enthusiasts

## Why This Product

- Trusted hagen brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Effortless Readability:** Large, clear markings with ideal salinity range highlighted for quick checks.
- • **Portable & Permanent Use:** Use it as a permanent fixture or a handy portable tester for flexible monitoring.
- • **Precision Salinity Control:** Maintain perfect marine conditions with reliable specific gravity readings.
- • **Seamless Aquarium Integration:** Slim, minimalist design blends invisibly into your tank’s aesthetic.
- • **Trusted Marine Health Essential:** Keep your marine fish and invertebrates thriving with stable salinity levels.

## Overview

The Fluval Sea Hydrometer is a compact, glass device designed for marine aquariums to accurately measure specific gravity and salt levels. Featuring large, easy-to-read markings and a slim profile, it can be permanently installed or used portably, ensuring stable salinity for optimal marine life health.

## Description

Fluval Sea Hydrometer provides an accurate and convenient method of measuring specific gravity and salt level in marine aquariums. Regular testing is strongly recommended as stable salinity levels are essential for the health of marine fish and invertebrates. Compact and easy to use, the hydrometer can be permanently installed inside the tank for continuous readings. Its slim, low-profile design 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 it in the water. The Fluval Sea Hydrometer features large, easy-to-read markings with ideal salinity range clearly marked in green for clarity.

Review: Affordable and accurate! - Works great when I calibrate with freshwater and put in but I don’t leave it in my tank, that might not work, but the way I use it to test my water it’s been perfect I love it! Very affordable and seems accurate!!!
Review: Disappointed.... - I already have one of these and it works great. I have a couple specimen specific tanks so I wanted to get one for each tank so I'm not always having to move them or put my hand in to do it. I ordered 2 more and both these new ones don't work. Rinsed them with fresh water and even rinsed them out with vinegar and still they don't work. I can see air bubbles on the armature and tried gently taping as per the instructions, the bubbles don't disperse. I never had this trouble with the one I have, it worked great from the get go and I've loved having it. I've had to rinse it once and awhile and even had debris get in it so I'd rinse it out and it was fine. I have a regular hydrometer that I use when mixing salt water so I've compared my first one with it and it's alway been pretty accurate. It was a no brainer to get the same brand, guess I was wrong. I'm disappointed with this purchase. I'll try soaking them in vinegar like other people suggested but more than likely I'll return them. If soaking works then I'll update my review.

## Features

- Helps measure specific gravity and salt level in marine aquariums
- Features large, easy to read markings
- Simple design-blends in easily
- Item Package Weight: 0.185

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B007MM0YUU |
| ASIN  | B007MM0YUU |
| Additional Features | Large Easy-to-read Markings, Simple Design, Marine Aquariums |
| Best Sellers Rank | #139,817 in Pet Supplies ( See Top 100 in Pet Supplies ) #25 in Aquarium Hydrometers |
| Brand Name | Hagen |
| Color | green |
| Customer Reviews | 3.7 3.7 out of 5 stars (825) |
| Date First Available  | March 2, 2012 |
| Department  | men, women |
| Global Trade Identification Number | 00015561143561 |
| Is Discontinued By Manufacturer  | No |
| Item Dimensions L x W x H | 1"L x 5.5"W x 7.9"H |
| Item Shape | Rectangular |
| Item Weight | 23 Grams |
| Item model number  | 14356 |
| Manufacturer | Rolf C. Hagen (USA) Corp. |
| Manufacturer  | Rolf C. Hagen (USA) Corp. |
| Manufacturer recommended age  | 1 month and up |
| Material Type | Glass |
| Model Number | 14356 |
| Product Dimensions  | 1 x 5.5 x 7.9 inches; 0.81 ounces |
| Product Style | Classic |
| Specific Uses For Product | Marine Aquariums |
| Tank Volume | 35 Liters |
| Target Species | Fish |
| UPC | 015561143561 |
| Unit Count | 1.00 Count |
| Vivarium Type | Aquarium |

## Product Details

- **Brand:** Hagen
- **Color:** green
- **Item Weight:** 23 Grams
- **Material:** Glass
- **Product Dimensions:** 1"L x 5.5"W x 7.9"H
- **Shape:** Rectangular
- **Special Feature:** Large Easy-to-read Markings, Simple Design, Marine Aquariums
- **Specific Uses For Product:** Marine Aquariums
- **Style:** Classic
- **Tank Volume:** 35 Liters

## Images

![Fluval Sea Hydrometer for Aquarium, Medium - Image 1](https://m.media-amazon.com/images/I/81Zk0yoggSL.jpg)
![Fluval Sea Hydrometer for Aquarium, Medium - Image 2](https://m.media-amazon.com/images/I/61M8zDiiIBL.jpg)
![Fluval Sea Hydrometer for Aquarium, Medium - Image 3](https://m.media-amazon.com/images/I/41h+BPNIRtL.jpg)
![Fluval Sea Hydrometer for Aquarium, Medium - Image 4](https://m.media-amazon.com/images/I/41jolZz6lLL.jpg)
![Fluval Sea Hydrometer for Aquarium, Medium - Image 5](https://m.media-amazon.com/images/I/51kUcWOxu8L.jpg)

## Customer Reviews

### ⭐⭐⭐⭐⭐ Affordable and accurate!
*by C***S on August 19, 2025*

Works great when I calibrate with freshwater and put in but I don’t leave it in my tank, that might not work, but the way I use it to test my water it’s been perfect I love it! Very affordable and seems accurate!!!

### ⭐ Disappointed....
*by M***H on April 29, 2017*

I already have one of these and it works great. I have a couple specimen specific tanks so I wanted to get one for each tank so I'm not always having to move them or put my hand in to do it. I ordered 2 more and both these new ones don't work. Rinsed them with fresh water and even rinsed them out with vinegar and still they don't work. I can see air bubbles on the armature and tried gently taping as per the instructions, the bubbles don't disperse. I never had this trouble with the one I have, it worked great from the get go and I've loved having it. I've had to rinse it once and awhile and even had debris get in it so I'd rinse it out and it was fine. I have a regular hydrometer that I use when mixing salt water so I've compared my first one with it and it's alway been pretty accurate. It was a no brainer to get the same brand, guess I was wrong. I'm disappointed with this purchase. I'll try soaking them in vinegar like other people suggested but more than likely I'll return them. If soaking works then I'll update my review.

### ⭐⭐⭐⭐⭐ Works well with proper maintenance
*by K***N on June 25, 2025*

Works well and is accurate as long as you flush it with freshwater afterwards or else the reading will start to become off due to salt buildup.

## Frequently Bought Together

- Fluval Sea Hydrometer for Aquarium, Medium
- Instant Ocean Sea Salt 50 Gallons, For Marine Aquariums, Fast Dissolving
- API SALTWATER MASTER TEST KIT 550-Test Saltwater Aquarium Water Test Kit

---

## Why Shop on Desertcart?

- 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016
- 🌍 **Shop Globally** — Access 737+ million products across 21 categories
- 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price
- 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members)
- 🔒 **Secure Payments** — Trusted payment options with buyer protection
- ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews

**Shop now:** [https://www.desertcart.co.uk/products/6541540-fluval-sea-hydrometer-for-aquarium-medium](https://www.desertcart.co.uk/products/6541540-fluval-sea-hydrometer-for-aquarium-medium)

---

*Product available on Desertcart United Kingdom*
*Store origin: GB*
*Last updated: 2026-05-14*