Low salinity

[liquid_wind]

I bought an existing system that had a few fish (couple gobies and a chromis) Where I live, the local aquarium offers free water, which I have done a couple water changes with and the previous owner used their water as well. Everything seems to be going well, fish healthy, actively feeding. However my refractometer came in today, I calibrated it with RO water and the aquarium reads at 1.019 SG. I then tested the water I was about to use for the next water change, and again 1.019... This seems low, but everything is doing well. Is the refractometer off? Is it fine so long as I keep it consistently at this reading?

Any advice appreciated!

 

[fishyguy7]

First you should get some calibration fluid for your refractometer. Using RO water is not ideal. Secondly if this is a fish only system it's not unheard of to keep the salinity that low. Before you make any changes get some of the calibration fluid then go from there.

 

[liquid_wind]

Alright, the manual didn't mention that, I'll order some. Thanks!

And yeah, it will either end up FOWLR or some Zoas, no more than that though.

 

[zachfishman]

First you should get some calibration fluid for your refractometer. Using RO water is not ideal. Secondly if this is a fish only system it's not unheard of to keep the salinity that low. Before you make any changes get some of the calibration fluid then go from there.

+1 Be sure to use calibration solution.

+2 Yes, FO and FOWLR systems are just fine at lower salinities. At work I keep our non-invert systems at 20ppt (1.015 sg).

 

[Khazmodain]

Yep definitely use calibration fluid. As fishyguy7 said, that's not out of the question for a fish only system. Aim for something higher (32-35 ppt) if you're going to add inverts or corals though.

 

[mcgyvr]

Some are meant to be calibrated with 35ppt calibration fluid..some are meant to be calibrated with ro water.. Follow the manual..
Many fish stores maintain lower salinity as they can save money on salt as well as a belief that its helpful against parasites,etc... Its not out of the ordinary to hear a story like this at all...
Typically its best to maintain at natural levels but many times you can run lower without any problems in a fish only setup..
You can slowly raise it over the course of a few weeks by putting salt water in your ato container or other methods..

 

[Uncle99]

In lower salinities, it is easier for fish to respirate as more oxygen is disolved in the water.
This leads to potentially healthier fish through the shipping/holding/selling process as less stress.

But I agree with Mcgyvr, not natural, I might go 1.023, but NSW values in the end are best.