Salt mix salinity droping

[DangerClose]

Hi all. I just got done mixing my first batch of salt water. I got it to 35 ppt.
I have been running my tank for a few hours now and the salinity has dropped to 32 ppt. Is that normal or is my salt mix seperating.
I do have some white dust gathering in my sump, but its hard to tell if its just dust from my white reef rock or the salt seperating from the water

 

[ariellemermaid]

Hi all. I just got done mixing my first batch of salt water. I got it to 35 ppt.
I have been running my tank for a few hours now and the salinity has dropped to 32 ppt. Is that normal or is my salt mix seperating.
I do have some white dust gathering in my sump, but its hard to tell if its just dust from my white reef rock or the salt seperating from the water

That sounds fairly unusual. How are you measuring your salinity, and are you correctly adjusting for the difference in temperature? Hanna checker does this automatically for instance. Also, did you mix it until clear, and follow the minimum mixing time listed on the box? If the measurements are good, I can only imagine that perhaps it wasn’t fully mixed during that initial measurement. I mix with a strong pump and can get Fritz clear in about 45 minutes, however they recommend mixing for at least 2 hours so that’s when I do my first test.

 

[DangerClose]

That sounds fairly unusual. How are you measuring your salinity, and are you correctly adjusting for the difference in temperature? Hanna checker does this automatically for instance. Also, did you mix it until clear, and follow the minimum mixing time listed on the box? If the measurements are good, I can only imagine that perhaps it wasn’t fully mixed during that initial measurement. I mix with a strong pump and can get Fritz clear in about 45 minutes, however they recommend mixing for at least 2 hours so that’s when I do my first test.

 

[DangerClose]

I used Red Sea Coral Pro. It said not to mix for more than 2 hours and I mixed everything for at least 90 minutes and until it as clear. I am measuring with a plastic needle float

 

[ariellemermaid]

I used Red Sea Coral Pro. It said not to mix for more than 2 hours and I mixed everything for at least 90 minutes and until it as clear. I am measuring with a plastic needle float

Here is what I have for coral pro:

It sounds like your mixing procedure should have been adequate. It’s interesting though that they want you to raise the temp after mixing and before taking the measurement though rather than just correcting for temperature, but I suppose the change in temp could affect precipitation a bit.

It sounds like you’re using a hydrometer. These have fallen out of favor because refractometers are more accurate and usually adjust for temperature in the device, but they’re a little more expensive. With a hydrometer you have to do some of the work.

I’m going to assume you mixed cold, took a measurement, then added the water to the tank, heated it up, and checked again. More assumptions for these calculations: your cold water is about 67 degrees, your tank is set to 77, and your hydrometer is calibrated for 77F. If you measure 35ppt on the cold water the temperature correction would yield an actual salinity of about 33ppt. Then when you take the second measurement on the warm water that’s what you’d find- 33ppt. Could something like that he going on here? Not the exact numbers of course, but the difference in temperature between mixing container and tank. Here is a hydrometer temperature conversion calculator.

 

[Karen00]

I agree, buy a refractometer or a digital salinity pen. Are you bringing the salt up to temp in your mixing bucket? The first step is to mix it cold to 35ppt (if that's your desired salinity) then bring the mixing bucket up to the same temp as your tank. Once your mixing bucket is up to temp then measure the salinity again. You'll probably find it has dropped a couple points. Now you add more salt to the mixing bucket to bring it back up to 35ppt. You might want to let it sit a bit longer at temp and measure it again before adding it to your tank to ensure it's still the correct salinity. It's important to make sure your mixing bucket is brought up to the same temp as your tank to ensure the salinity matches. Temperature affects salinity.