Accurately Measure Your Aquarium's Specific Gravity with Instant Ocean SeaTest Hydrometer

Marc Kenemuth: Received item that was ordered. Will use seller again

United States on Jan 18, 2023

JQ: bad quality and package

Canada on Dec 08, 2021

Allison C: Didnt work as well as my old one. Bubbles get trapped under the needle and give inaccurate readings. Ive done everything to keep this from happening but it continues. Switching to a refractometer

Canada on Jun 17, 2019

Catherine M.: The best hydrometer for salt tank!

Canada on Apr 26, 2019

Amazon Customer: Perfect item just what I needed thanks

Canada on Mar 27, 2017

John: This is the second hydrometer of this model that I've owned (they do get erratic over time even when rinsed and stored with RO water, I think because the pivot point wears and also gets precipitate on it). The previous one read one point high, while this one is accurate.

Any plastic swing-arm hydrometer will have issues with air bubbles sticking to the arm when the hydrometer is new -- that's often why people have issues with these things. I soak mine in salt water for about three days, rinsing with RO each day then refilling. That seems to remove the film on the plastic that attracts the air bubbles.

Swing arm hydrometers also should be checked for accuracy. I calibrate them against a (properly calibrated) refractometer. Once I determine how high or low the hydrometer reads, I make a note of that (I use a permanent marker to note on the back of the hydrometer, e.g. "This hydrometer reads 1 ppt high"). Then I have an easy to use, accurate device to do routine checks of salinity (well, actually specific gravity). The more tedious-to-use refractometer is used for periodic sanity checks.

United States on Oct 25, 2016

Michael: i use this for 2 different tanks and have gotten consistent results. the only thing to watch for is bubble on the needle. they will cause significant differences in the reading. on my brackish tank it was showing higher salt then my salt tank due to bubble. just give it a small tap and the bubble comes off and the reading is perfect.

for the money its hard to find a better product

United States on Aug 08, 2015

Datboiconnor: This is a decent measurement tool to see if my tanks salinity is in the right place. I would not recommend this for precise measurements only because it is affected by current, bubbles and salt crystals left behind from previous testing. Make sure you rinse it with tap water to get rid of the salt crystals so it don't affect the next testing. Then dry it out and you should be good. Make sure its level with the ground otherwise your results will be affected.

Pros
-Good for a general measurement
-Easy to use

Cons
-Multiple factors may affect your end result but with a little care it preforms well
-Clean after usage

United States on Aug 06, 2015

MrRich: I happen to live near the ocean,, so I have the luxury of testing it against a control system. I took several samples of ocean water at various depths and away from shore to see what the actualy salinity was. Then I made a mark on it to set the salinity of my fish tank.. (.038) anyway,, I live in the south pacific in the marshall islands.. It seems a little high,, so either the gauge is slightly wrong or the water has more salt than what wikipedia says it should be for the tropics.

United States on Feb 06, 2014