IO Reef Crystals giving incorrect values

[EbiAqua]

Since I set up my small 7g reef I have used IO Reef Crystals as my salt of choice since it is widely available. However, I have noticed I get wildly inconsistent results when mixing new batches of saltwater. For example, the instructions say 1/2 a cup of salt per gallon should produce a specific gravity of 1.021. However, in my last batch of 4 gallons, using 2.5 cups (roughly the amount ChatGPT calculated to get a SG of 1.026), yielded a result of 1.022.

I am allowing my salt to mix overnight and I recalibrate my refractometer with distilled water before every salinity test.

It is annoying having to constantly guess how much salt I need to add, recalibrate, test, and adjust. It makes water changes a huge pain in the you-know-what when I can't just add salt to water and know I'll get consistent results; I have had readings as low as 1.017.

Any advice is appreciated.

 

[56longroof]

Interesting. I've never had a single issue with Reef Chrystals.

 

[EbiAqua]

Interesting. I've never had a single issue with Reef Chrystals.

Since I live in Florida, my salt became a solid block at some point due to absorbing ambient humidity, despite sealing the bag and keeping it stored in a container with a lid. Would absorbing moisture from the air have anything to do with the results?

 

[56longroof]

Since I live in Florida, my salt became a solid block at some point due to absorbing ambient humidity, despite sealing the bag and keeping it stored in a container with a lid. Would absorbing moisture from the air have anything to do with the results?

It may not be fully dissolving since it's clumped up. Have you tried to put a powerhead in the mixing container?

 

[56longroof]

Since I live in Florida, my salt became a solid block at some point due to absorbing ambient humidity, despite sealing the bag and keeping it stored in a container with a lid. Would absorbing moisture from the air have anything to do with the results?

What temp are you checking salinity at? I heat my mixing barrel to 77° before checking.

 

[EbiAqua]

It may not be fully dissolving since it's clumped up. Have you tried to put a powerhead in the mixing container?

I have one in my bucket constantly circulating the mix, and I give the bag a few smacks on my tile floor to make sure it isn't clumped up before adding any to the bucket.

 

[EbiAqua]

What temp are you checking salinity at? I heat my mixing barrel to 77° before checking.

I have the hottest room in my house and it is practically summer, so the ambient temp of my room is between 76 and 78. I don't keep a heater in my bucket at the moment.

 

[Ziggy17]

I think the calibration is the issue. You shouldn’t be calibrating at zero if my memory is correct. Try calibrating the refractometer with 35ppm solution. Randy has a DIY calibration recipe in here somewhere.
Otherwise, I’d suggest buying a TM hydrometer. It’s the best piece of gear you will buy under $50. Otherwise use that solution to calibrate and you should accurate results.

 

[Euphylliaphyle]

Since I live in Florida, my salt became a solid block at some point due to absorbing ambient humidity, despite sealing the bag and keeping it stored in a container with a lid. Would absorbing moisture from the air have anything to do with the results?

Moisture is not salt, but it adds mass. You may be adding considerably less salt for a given weight of salt mix, resulting in a weak mix.

 

[EbiAqua]

Update:

I now go by an agreed upon measurement by weight for IORC to get a specific gravity of 1.026, which is 154.65g of salt per gallon. I mix this in, adding slightly more than necessary, measure my salinity after 24 hours, then calculate the amount of RO to add in order to get my target salinity. I use calculators on Hamza's Reef now, as ChatGPT is stupid and gives wildly different results for the exact same query!

I still calibrate my refractometer at 0.000 with distilled water. My tank's salinity sits between 1.025 and 1.026.

Thank all of you for your input, I've learned a lot about reefing these last 10 months.