Salinity dropping - mystery

[Rangachick]

Hi everyone,
We have a bit of a mystery on our hands. Our tank is relatively new and salinity has been running at 1.021 (and we want to gradually increase this to 1.025). We recently added an Aqua Medic skimmer (last Saturday) and ever since, the salinity of the tank has been slowly dropping. Today's reading (using a Serenity MS-31 digital hydrometer) is sitting at 1.018 and last night it was at 1.019 We have tested the hydrometer in distilled water so I think it is working correctly.
Anyway, to help with the drop, we replaced 15 litres with 1.025 saltwater and have repeated this step this morning. We have also replaced the ATO tank with salt water instead of fresh water.
Not sure if we are doing the right thing or not and certainly do not want to stress out our fish. Any advice would be greatly accepted.

 

[hllb]

Get calibration fluid for the hydrometer to test it rather than on distilled water.

 

[AllSignsPointToFish]

Sounds like you're on the right course. I know nothing about the MS-31 hydrometer, so I can't help you with that. Can you take a sample to the LFS for testing?

And welcome to R2R!

 

[Dom]

Hi everyone,
We have a bit of a mystery on our hands. Our tank is relatively new and salinity has been running at 1.021 (and we want to gradually increase this to 1.025). We recently added an Aqua Medic skimmer (last Saturday) and ever since, the salinity of the tank has been slowly dropping. Today's reading (using a Serenity MS-31 digital hydrometer) is sitting at 1.018 and last night it was at 1.019 We have tested the hydrometer in distilled water so I think it is working correctly.
Anyway, to help with the drop, we replaced 15 litres with 1.025 saltwater and have repeated this step this morning. We have also replaced the ATO tank with salt water instead of fresh water.
Not sure if we are doing the right thing or not and certainly do not want to stress out our fish. Any advice would be greatly accepted.

I prefer refractometers..

Refractometer for Reading Salinity with Calibration Fluid

Why does BRS recommend this? If you have been using a hydrometer and have never tried a refractometer then you should really invest in one. They use much less water, and can easily be calibrated for accurate repeatable readings. For the most accurate readings you will want to calibrate the...

www.bulkreefsupply.com

You don't want to use salt water in your ATO. Once you reach the desired level, you have to empty the ATO of the salt water or else your salinity will go over the top.

 

[AllSignsPointToFish]

+1 for refractometers. I use a Milwaukee refractometer. Very good investment!

 

[Rangachick]

Get calibration fluid for the hydrometer to test it rather than on distilled water.

Thank you - I'll order some now and let you all know how I go.

 

[hllb]

Thank you - I'll order some now and let you all know how I go.

Sorry, I misread and thought you had a refractometer. I don’t know if there is a way to calibrate a hydrometer. Maybe take a sample to a local fish store to verify your salinity.

 

[Rangachick]

Sounds like you're on the right course. I know nothing about the MS-31 hydrometer, so I can't help you with that. Can you take a sample to the LFS for testing?

And welcome to R2R!

Thank you. Unfortunately our LFS is 1.5 hours away but the owner is fabulous and very helpful. We live in a little town called Forbes in the central west region of New South Wales (Australia) which is about 6 hours drive to the coast lol. I will take the advice of others and but some calibration fluid and see if that makes a difference.

I prefer refractometers..

Refractometer for Reading Salinity with Calibration Fluid

Why does BRS recommend this? If you have been using a hydrometer and have never tried a refractometer then you should really invest in one. They use much less water, and can easily be calibrated for accurate repeatable readings. For the most accurate readings you will want to calibrate the...

www.bulkreefsupply.com

You don't want to use salt water in your ATO. Once you reach the desired level, you have to empty the ATO of the salt water or else your salinity will go over the top.

Thanks Dom. Yes - we will keep a close eye on our levels and as soon as it's starting to climb again, we'll switch back over to freshwater.

 

[AllSignsPointToFish]

Thank you. Unfortunately our LFS is 1.5 hours away but the owner is fabulous and very helpful. We live in a little town called Forbes in the central west region of New South Wales (Australia) which is about 6 hours drive to the coast lol. I will take the advice of others and but some calibration fluid and see if that makes a difference.

Thanks Dom. Yes - we will keep a close eye on our levels and as soon as it's starting to climb again, we'll switch back over to freshwater.

I'd definitely invest in a refractometer if you can afford it. I not only use it to test tank water but also water-change water as I'm adding salt. I also use it to monitor salinity in quarantine tanks. I highly recommend one!

 

[ca1ore]

Yup, hydrometers perform poorly. First step is to confirm the salinity drop with a better instrument. If you do confirm the drop, then you have to figure out where the salt is going. Since only pure water evaporates, there’s either a leak somewhere or it’s leaving in your skimmate.

 

[Rangachick]

Thanks all for the feedback. I am happy to purchase a refractometer and see that the Red Sea one sells here in Australia for approx AUD$120 and there are others that can be purchased for as little as AUD$30. Does anyone have experience with the Red Sea refractometers - are they as good (and worth the money) as the reviews suggest?

 

[Dom]

Yup, hydrometers perform poorly. First step is to confirm the salinity drop with a better instrument. If you do confirm the drop, then you have to figure out where the salt is going. Since only pure water evaporates, there’s either a leak somewhere or it’s leaving in your skimmate.

Interesting. I've never heard of this happening. In thinking about it, it makes sense to me that this could happen. I wonder why you don't hear about this more often.

 

[Dom]

Thanks all for the feedback. I am happy to purchase a refractometer and see that the Red Sea one sells here in Australia for approx AUD$120 and there are others that can be purchased for as little as AUD$30. Does anyone have experience with the Red Sea refractometers - are they as good (and worth the money) as the reviews suggest?

That's about $85 US. Is the one I linked available to you? It isn't a Red Sea but it works well for a fraction of the price.

 

[Phil D.]

Thanks all for the feedback. I am happy to purchase a refractometer and see that the Red Sea one sells here in Australia for approx AUD$120 and there are others that can be purchased for as little as AUD$30. Does anyone have experience with the Red Sea refractometers - are they as good (and worth the money) as the reviews suggest?

I have the Red Sea refractometer and only need to calibrate it once a month and I use it every week when mixing saltwater.

 

[ca1ore]

Interesting. I've never heard of this happening. In thinking about it, it makes sense to me that this could happen. I wonder why you don't hear about this more often.

Less of a problem if you dry skim; more of a problem if you wet skim. I keep my AWC water at a slightly higher salinity than the tank as an offset.

 

[Rangachick]

Thanks everyone - ended up with the Red Sea refractometer and guess what....salinity is higher than it should be! Baby steps now to reduce it to 1.025.