AccuBrate Refractometer and Hydrometer Salinity Calibration Fluid – 250 ml Solution to Accurately Calibrate Refractometer and Hydrometer for Testing Natural Saltwater or Synthetic Sea Water (250 ml)

Happy with the product needed to test the salinity of the water inputting in to the saltwater tank during water changes it works fine i dont really have any complaints was recommended the product from a coworker at a coral shop

This is a good item safe for your fish.

Like others reviewers, my bottle only clocked in at 30ppy. Checked against Tropic Marin precision hydrometer. This was after shaking well and trying several attempts.I see great reviews for the smaller bottle. This was the large bottle.Why 3 stars? Because it was pretty consistent to 30ppt, which if you know this, can still use it to calibrate your refractometer. But you could throw 25ppt if you trust it as being 35ppt as stated. Use with caution, and multiple references. I returned due to false advertising

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I recently bought a digital refractometer and tested this product. This product is not 35ppt. I tested the calibration solution that came with my Milwaukee refractometer. That one reads at 37ppt which is a know issue (has a margin of 2ppt). I’ve mixed a fresh batch with red sea salt and weighed out everything to get it at exactly 35ppt at 77degrees. It read on my digital refractometer as 36ppt. I still need to fine tune it as temperature is also a factor but I’m testing my water now at 35ppt to get roughly around 1.025. This calibration fluid measures waaaaaay off (31ppt).

Works like a charm - just ensure to set your refractometer down for a few minutes so the temperature equalizes before making any changes. A+

I have not tried it yet but was unhappy that the bottle was unsealed and the cap was loose. It was in a sealed zip lock bag and part of the solution had spilled out into the bag leaving me with a 3/4 full bottle.

Without lab calibrated equipment how accurate is it really going to be. so far it seems to help get a accurate reading. Still probably a good idea to send a water sample into a company for lab quality results.