Salinity dropping with evaporation (FRITZ BLUE BOX)

[YHSublime]

Yes, you read right. For the most part it's staying in a range that it should, but I recently had an ATO malfunction into a very small tank, and the parameters have gotten haywire ever since. 

 

Let me start with this: The first thing I did was check my calibration on my refractomer... it's all good. 

 

This caused me to check my other tank, which I'm currently manually topping off and dosing, same thing, the salinity is dropping. Now on this tank, the usual suspects are out the door: New tank, so no leaks, I'd notice. Not skimming dry enough to worry about salinity dropping. And no ATO hooked up. 

 

So I go and check my salt mixing bucket, and normally over time, the saltwater in there has the salinity rise... and it's actually lower again. 

 

The only thing I can think of culprit wise is I have swapped salt, from IO to Fritz blue box. I'm figuring it's not leveling out properly? I mix at 75F, for 24 hours at least, and I have mixed up the bucket of salt (yes, you read that right as well, I guess you're meant to be stirring salt before you use it to make saltwater.)

 

Am I missing something? 

[Kathryn Lawson]

How did you determine the volume or mass of the new brand of salt to add when mixing the saltwater - the same as your old brand? It could be that the composition of the new mix is different (more anti-clumping agents? fillers? other compounds?), so you need to use more of the new brand than you did with the old brand to get to the same salinity.

[YHSublime]

4 minutes ago, Kathryn Lawson said:

How did you determine the volume or mass of the new brand of salt to add when mixing the saltwater - the same as your old brand? It could be that the composition of the new mix is different (more anti-clumping agents? fillers? other compounds?), so you need to use more of the new brand than you did with the old brand to get to the same salinity.

 

By following manufacturers instructions, 1/2 cup per gallon to get to 1.025

 

To be clear, I am achieving desired salinity, but for an unknown window. The same 25 gallons that read 1.025 this evening, will continue to do so within about a 24 hour period. But in the next 4 days it will be around 1.020

 

The anomaly here is the salinity lowering instead of rising on 3 independent containers. 

[DaJMasta]

It's not really physically possible to lose that much salt without being able to notice it - you should be seeing condensates or exported saltwater that would be 20% of the total volume for a 20% salinity drop, and I'm not sure just sucking all the alkalinity, calcium, and magnesium out of it would even account for everything.

 

You say you've rechecked your refractometer, but have you checked another tank with it right before/after your measurement of this tank/this new water?  Are the lighting conditions similar for the tests (for the see through type) and is the temperature of the tanks similar?

Everything I can think of points towards measurement error (and entirely possible the hardware's fault), but perhaps it's something like the initial measurement is being elevated somehow and it's settling to the lower value?  Are the directions on the new salt right in line with the old one (salinity should be the same with the same measured mass of salt added regardless of the composition as long as its all dissolving)?

[YHSublime]

3 hours ago, DaJMasta said:

It's not really physically possible to lose that much salt without being able to notice it - you should be seeing condensates or exported saltwater that would be 20% of the total volume for a 20% salinity drop, and I'm not sure just sucking all the alkalinity, calcium, and magnesium out of it would even account for everything.

 

You say you've rechecked your refractometer, but have you checked another tank with it right before/after your measurement of this tank/this new water?  Are the lighting conditions similar for the tests (for the see through type) and is the temperature of the tanks similar?

 

Yup, the refractometer is calibrated correctly. I have checked another tank outside of the mixing bucket at the same time, in the same lighting conditions. The temp might be a degree or two higher on the mixing station. 

 

3 hours ago, DaJMasta said:

Everything I can think of points towards measurement error (and entirely possible the hardware's fault), but perhaps it's something like the initial measurement is being elevated somehow and it's settling to the lower value?  

 

This is the only thing I can think of, I just don't know how it could settle to a lower value? I am at the end of my first 200 gallon batch box, and I'm a little worried about giving another 200 a go. 

 

3 hours ago, DaJMasta said:

(salinity should be the same with the same measured mass of salt added regardless of the composition as long as its all dissolving)?

 

The directions are right in line with the old salt, and I have 2 pumps on the mixing station. The water goes clear very quickly, and I confirmed there are no solids left behind on the bottom. It's dissolving properly. 

[YHSublime]

From what I can tell, it's mixing at 1.025, clear, nothing in solution, and then over the next few days it continues to drop a few points. I did move the bags from a box and pour them into a bucket, I don't know if that has any effect. 

 

Either way, looks like I've gotta wait a few days until I do water changes after mixing salt, not a problem. FWIW, I pulled the ATO off the tank and it leveled out after 2-3 days of evap, I had a few pieces of SPS brown out, but they should bounce back in no time. I have ATO hooked back up and salinity and alk have been rock solid for the past week since this post. 

[BowieReefer84]

I didn’t read this thread (posting from phone). Fritz blue box is trash. I was having tank issues after I spiked my Alk (my fault). As part of the “trying to get back to normal” I did a ICP test on freshly mixed blue box to see where it landed and Alk came back at 6.2 when salinity was 35ppm. I tested Alk myself with a Hanna checker and also got 6.2. I can send you all the test results for parameters. I’m going to reef crystals. Available at Petco locally and cheap to order online in store pickup.