After following the instructions exactly on Red Sea Coral Pro salt, salinity is VERY low

golgobot

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I followed the instructions on the salt mix to get to a salinity of 35ppm. I weighed the exact amount to place into 35 gallons of RODI water (it comes out to about 1/2 cup per gallon of water). I mixed it for a few hours. When I test the salinity it comes out to 29ppt! It's way off!

The mixing station is in my basement and I know temperature effects salinity. The water comes out to about 65°F. Does temperature effect salinity that much to be off by over 15%?

Should I get a heater to install permanently in my mixing tank?

I'm not sure what else I'm doing wrong here.

Thanks!
 

fade2black

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I use a heater in mine, just because when I do a water change I want the temps to be as close as possible.

What are you using to measure salinity? Are you sure it's accurate?

Honestly, I never follow the directions on the box, I add until I get the salinity I want and have never compared it to what they say I should add. lol
 

fade2black

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Also, here is the effect of temp on salinity.

 

58e970b2-3f88-4897-87ba-5

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What are you measuring with?
Some devices auto correct for temperature variation.

I have found with Tropic Marin and Instant Ocean salt, more is required than they state to get to 35ppt. It is a pain, an accurate recipe could make mixing so much easier.

I mix cold and heat it closer to when I want to use it.
 

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check your salinity tester or get one like the hanna because it will factor temp into the reading automatically. standard for most salt I have used is 1/2 cup per gallon so something is off
 
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I use a heater in mine, just because when I do a water change I want the temps to be as close as possible.

What are you using to measure salinity? Are you sure it's accurate?

Honestly, I never follow the directions on the box, I add until I get the salinity I want and have never compared it to what they say I should add. lol
Thanks for the reply! I use a refractometer, which I calibrate against a 35ppm solution every time I measure my mix. Red Sea says that the water shouldn't be heated up because it can cause precipitation of calcium and carbonate.

I'm just confused why the packaging g/L recommendation is so wrong. I didn't even eyeball the volume, I measured the weight with a food scale.
 
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golgobot

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check your salinity tester or get one like the hanna because it will factor temp into the reading automatically. standard for most salt I have used is 1/2 cup per gallon so something is off

Interesting. I thought the refractometers were calibrated for room temperature water. I've read that it helps to let the water sit on the refractometer for a couple minutes before taking the measurement.
 

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Thanks for the reply! I use a refractometer, which I calibrate against a 35ppm solution every time I measure my mix. Red Sea says that the water shouldn't be heated up because it can cause precipitation of calcium and carbonate.

I'm just confused why the packaging g/L recommendation is so wrong. I didn't even eyeball the volume, I measured the weight with a food scale.
I heat as well, based on wanting to add new water at the parameters including temp. I'm far from a chemist, but that seems like an odd reasoning by RedSea, considering the tank will be the same temp. Following this, looking to learn from others, why that recommendation is on the label.
 

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Interesting. I thought the refractometers were calibrated for room temperature water. I've read that it helps to let the water sit on the refractometer for a couple minutes before taking the measurement.
Might be worth taking a cup full in a bag and letting the tank/sump bring it to temp and then run a test.
 

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Interesting. I thought the refractometers were calibrated for room temperature water. I've read that it helps to let the water sit on the refractometer for a couple minutes before taking the measurement.
refractometers yes but with the hanna no. Since I got the Hanna I have not touched the refer. I have this one and its pricey but you get the salinity and temp, they are super accurate and if you make a lot of salt water its worth it.
 
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refractometers yes but with the hanna no. Since I got the Hanna I have not touched the refer. I have this one and its pricey but you get the salinity and temp, they are super accurate and if you make a lot of salt water its worth it.
Thanks. Suppose an extra $50 in the grand scheme of things is nothing compared to everything else lol.
 

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Thanks. Suppose an extra $50 in the grand scheme of things is nothing compared to everything else lol.
Trust me it is! This is coming from someone who has a 1 income family with two kids. I am super stingy and broke (two things that make this hobby a 8!tch) and It is one of the most used pieces of testing equipment besides the alk checker. I do weekly water changes and its always 1/2 cup per gallon ( Red sea blue bucket currently) I only test when I know everything is mixed properly and its always spot on. Just so you know where my info is coming from I am not just BSing here is my tank
 

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Thanks for the reply! I use a refractometer, which I calibrate against a 35ppm solution every time I measure my mix. Red Sea says that the water shouldn't be heated up because it can cause precipitation of calcium and carbonate.

I'm just confused why the packaging g/L recommendation is so wrong. I didn't even eyeball the volume, I measured the weight with a food scale.
How are you using a food scale to determine a volume measurement?

Once you open that bucket, the salt will begin to absorb moisture. This means that the same volume measurement will increase in weight over time.
 

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Interesting. I thought the refractometers were calibrated for room temperature water. I've read that it helps to let the water sit on the refractometer for a couple minutes before taking the measurement.
Remember, it's only a single drop of water. It doesn't take long for it to reach equilibrium with the room temp.
 
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Trust me it is! This is coming from someone who has a 1 income family with two kids. I am super stingy and broke (two things that make this hobby a 8!tch) and It is one of the most used pieces of testing equipment besides the alk checker. I do weekly water changes and its always 1/2 cup per gallon ( Red sea blue bucket currently) I only test when I know everything is mixed properly and its always spot on. Just so you know where my info is coming from I am not just BSing here is my tank

Wow beautiful colors! I'm just about to cycle my tank after I get the parameters correct. Hopefully mine will look as nice as yours. Check out my build thread if you're curious.
 
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How are you using a food scale to determine a volume measurement?

Once you open that bucket, the salt will begin to absorb moisture. This means that the same volume measurement will increase in weight over time.

I'm using the scale to measure how many grams of salt I need for 35 gallons of water. Volume wise, it ended up being 1/2 cup per gallon of water.

How much can volume change due to moisture?
 

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I followed the instructions on the salt mix to get to a salinity of 35ppm. I weighed the exact amount to place into 35 gallons of RODI water (it comes out to about 1/2 cup per gallon of water). I mixed it for a few hours. When I test the salinity it comes out to 29ppt! It's way off!

The mixing station is in my basement and I know temperature effects salinity. The water comes out to about 65°F. Does temperature effect salinity that much to be off by over 15%?

Should I get a heater to install permanently in my mixing tank?

I'm not sure what else I'm doing wrong here.

Thanks!

I used Red Sea and when I weighed mine it was near enough exactly correct, I would look at your salinity reader before the salt for the reason.
 

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Interesting. I thought the refractometers were calibrated for room temperature water. I've read that it helps to let the water sit on the refractometer for a couple minutes before taking the measurement.

30seconds at most is fine, especially tank temp water, if cold then maybe a little more, I highly recommend a Tropic Marin hydrometer, you don’t have to use it all the time as it’s a bit clumsy but it’s extremely accurate and good for a reference.
 

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30seconds at most is fine, especially tank temp water, if cold then maybe a little more, I highly recommend a Tropic Marin hydrometer, you don’t have to use it all the time as it’s a bit clumsy but it’s extremely accurate and good for a reference.
Doesn't a hydrometer require temperature correction or you need to measure at the temp the hydrometer is calibrated?
 

Reef.

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Doesn't a hydrometer require temperature correction or you need to measure at the temp the hydrometer is calibrated?

yes and no, it’s calibrated at 25c so the water needs to be 25c when you take the reading, my tank is 26c so time I pour 500mls into measuring cylinder it’s 25c, you can use a chart to get a reading if say the water was only 20c, you can also just measure it straight from the tank but the flow needs to be off to read it, you can also easily break the hydrometer in the tank on a rock etc but for all that the reading it gives is extremely accurate and it never needs calibrating, good to know your salinity is correct.
 

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