Typical Variation in Instant Ocean Mix?

[KingBlingTX]

I recently switched to IO salt based on Randy's observations about various salt mixes. However, with the two bags of salt that I have purchased (50G mix size) I have encountered what I think is fairly large variation in the two on freshly mixed batches. I mix up 5 gallons at a time. In order to get 35 ppt salinity I've determined I need to add 770g of salt. A powerhead mixes the saltwater for 24 hours before I test it. Here are the results I've seen:

The ALK is higher than I expected. Not sure what is standard deviation for salt mix. The big differences in Ca and Mg is what concerns me the most.

I've done searches on forums to see what is expected, but all I've seen is anecdotal statements like "big variations" or "never had any issues". Does anyone know if this is typical?

Thanks for any help. (BTW- I would like a salt mix that gives ALK~8, Ca~420, & Mg~1300. If there is a better option than IO, I'm open to suggestions.)

 

[ash9965]

have you tried IO reef crystals VS regular IO

 

[redfishbluefish]

Are all three of these batches from the same bag? You mention two bags....the first test from bag one and the second two from bag two???? Some possibilities:

1. Dry salt not mixed enough.
2. Test method variation.

What test kits are you using? And did you make these batches by weight (implied...770 grams) or by using a refractometer? Last one....tap water or RO/DI?

 

[Randy Holmes-Farley]

I do not believe those values reflect normal variations in IO.

It may reflect the problem of selecting out 5 gallons worth from a container that may have settled and so is not uniform across the bucket or bag. Salt mixes do settle in shipping and other movements, and this is known problem to solid sampling in general.

It would be better to do such tests on whole buckets or bags, or use a special device designed to sample from all parts of the container. There are many made for just this reason for various industrial powder sampling problems.

I'd also add that many people experience results can only be from testing error. I do not know if that is the case here, but it may be. For example, people reporting that magnesium rose or fell 200 ppm in a week or two in their tank, when that just isn't possible.

That all said, you may actually have an off batch. It does sometimes happen, if a lot more rarely than folks think (IMO).

 

[JimWelsh]

To minimize testing error, I suggest taking the average of three tests in a row for each. I know that's a lot of testing, but when you really want to know it *isn't* testing error, averaging multiple tests works really well. Sometimes, one test result might even be so far off from the others that it should be considered an "outlier", and ignored completely.

EDIT: FWIW, I was that one guy in the room that raised his hand during Richard Ross's talk about testing at MACNA in Denver when he asked, "How many of you got a test result you liked the first time? And how many of you then tested again?"

 

[Congaken]

Just ordered Red Sea Coral Pro salt mix...from SaltwaterAquarium.com...

 

[shred5]

Reef crystals has been this way for me too.. Been testing from bag to bag and massive swings. I am done with it, I have used it in the past no problem but now I have thrown out a few bags because calcium was off the chart.
I mean there was so much calcium I could not read it with my test kits.

 

[jason2459]

In testing various salts using the partial volume of the salt I've found to get as consistent as possible test results between batches that I needed to take samples from multiple locations and mix the salt mix up between samples.

 

[badonkadonk]

There are many potential sources of error when we hobbyists make measurements. In this case settling of the salt mix and stratification of the various particle sizes is likely the culprit - the error being a non-representative sample if the salt was not taken from various locations from the container. Statistically, you need at least 30 subsample locations to determine concentrations in a unit - say a bag or bucket of salt if there is heterogeneity in the material. And there is a big reason for heterogeneity in our salt mixes due to the varied particle sizes - the larger particles eventually make their way to top of the container and the finest particles to the bottom. The various salt mix components (NaCl crystals, the various Calcium and Magnesium salts, etc.) have different particle sizes. Think a box of cereal - the little crumbs on the bottom weren't put there, they settled out during handling of the box. So either mix the container well, take a lot of samples from all over the container (a stratified random approach would be called for here) if you're trying to determine if there's something off with the batch of salt mix, prior to measuring. And of course more sources of error in the test kits we use. But all said, as long as you're doing relatively small changes, even a particular batch of your salt solution is off it won't make any significant difference to the livestock. And if you are doing a bigger water change, then it's probably best to take extra care to really mix your bucket - or, if you're using pre-measured bags (like many now supply to mix up a Brute trash can-full, 44 gallons), use the whole bag and don't worry about it, just get it all in the mixing container at once. But I wouldn't throw any salt away due to a measurement being "off." Even caked-up, wet salt eventually dissolves to normal parameters as long as you use the whole container to mix into one batch.

 

[shred5]

There are many potential sources of error when we hobbyists make measurements. In this case settling of the salt mix and stratification of the various particle sizes is likely the culprit - the error being a non-representative sample if the salt was not taken from various locations from the container. Statistically, you need at least 30 subsample locations to determine concentrations in a unit - say a bag or bucket of salt if there is heterogeneity in the material. And there is a big reason for heterogeneity in our salt mixes due to the varied particle sizes - the larger particles eventually make their way to top of the container and the finest particles to the bottom. The various salt mix components (NaCl crystals, the various Calcium and Magnesium salts, etc.) have different particle sizes. Think a box of cereal - the little crumbs on the bottom weren't put there, they settled out during handling of the box. So either mix the container well, take a lot of samples from all over the container (a stratified random approach would be called for here) if you're trying to determine if there's something off with the batch of salt mix, prior to measuring. And of course more sources of error in the test kits we use. But all said, as long as you're doing relatively small changes, even a particular batch of your salt solution is off it won't make any significant difference to the livestock. And if you are doing a bigger water change, then it's probably best to take extra care to really mix your bucket - or, if you're using pre-measured bags (like many now supply to mix up a Brute trash can-full, 44 gallons), use the whole bag and don't worry about it, just get it all in the mixing container at once. But I wouldn't throw any salt away due to a measurement being "off." Even caked-up, wet salt eventually dissolves to normal parameters as long as you use the whole container to mix into one batch.

Absolutely not the problem with what I do since mine comes in a bags and I pour them into a bucket so they get mixed up.. They are without a doubt bad bags of salt.
Believe me I know what I am doing. These were not little swings from bag to bag where one bag read 400 calcium and the next was 430 which alone could be a error just in testing with hobby grade kits.
I am using a bag of salt where a test kit does not even change colors.
I test all new bags of salt since I had a bad bag of corallife salt like 20 years ago that almost killed my tank.

 

[jason2459]

Absolutely not the problem with what I do since mine comes in a bags and I pour them into a bucket so they get mixed up.. They are without a doubt bad bags of salt.
Believe me I know what I am doing. These were not little swings from bag to bag where one bag read 400 calcium and the next was 430 which alone could be a error just in testing with hobby grade kits.
I am using a bag of salt where a test kit does not even change colors.
I test all new bags of salt since I had a bad bag of corallife salt like 20 years ago that almost killed my tank.

Well, to me the first set of test results is the only one that seems wrong. The other two are well with in range of each other.

Edit: regarding the OP's results.

 

[shred5]

Well, to me the first set of test results is the only one that seems wrong. The other two are well with in range of each other.

Edit: regarding the OP's results.

Agreed.. 1/2 drop different of regiment could make swing that much..
From first batch to second yea not right.
Also could be a change in test kits. With salifert I have had swings in test kit from one to another that are like that. That is also why I always test my new test kit to my old and have a second and third brand of kit around.

 

[badonkadonk]

OK, it appears mixing/sampling is not the cause for your variation, but I was speaking more generally in that it should be considered. Also, the Ca and Mg look pretty high for IO, those look more like RC numbers, and that's where UPG saves some manufacturing cost - by adding less of these components, so perhaps they mislabled/mishandled a batch of RC for IO. Very unlikely but that's more likely than a batch making it past QC testing - though there are acceptable ranges for all parameters. Especially alk, that changes so quickly after you add water that I'd bet the acceptable range is fairly wide for most manufacturers. And again, if you're doing small water changes these differences don't mean squat (unless you're not dosing or keeping up with biotic and abiotic losses - eventually low numbers could catch up with you). Don't like the high alk? Aerate for a while or add some acid. The low Ca is the only real concern - though not sure how much above 1500 your Mg is, but I've had my Mg up to about 2000 during a bryopsis battle with no ill effects. I think there's a general consensus wrt success in reefkeeping, it's not the salt but nutrients and stability within normal seawater ranges. Not saying it's the case for you but I think lots of us (me especially) end up chasing the wrong "demons" - in my most recent case I was having a devil of a time with nitrate and things generally looking blech when I finally decided to cast out a large neon devil's hand leather coral I've had for 10 years and my system almost instantly turned around. But that's not to say your salt is not giving you issues, it's just IME it turns out to be something else - usually.

 

[KingBlingTX]

Thanks for all the input! Reading through everyone's comments, the primary thing that stuck out in my mind was the possible phase separation of the mixture based on different bulk densities of the components. (I'm familiar with this phenomenon in my industry with what we call "salt & pepper" blends of polymers.) I wasn't aware this was an issue in these salts mixes. I'll be sure to address this in future mixes to see if that is the problem.

The primary concern I had was with Ca & Mg differences between the first bag and the second. To some extent, the difference in ALK was a concern too. I hadn't been recording the numbers for the first several tests on the first bag, but the ALK was generally between 8.5 & 9.5. I had already picked up some MA to add to bring down the ALK some.

I don't believe it is a result of test error. I am using same test kits for these results. Salifert for Ca & Mg. Red Sea Pro for ALK. I did 3 repeats on these tests because I was concerned about results. (Oddly enough, just a couple of weeks ago I did a series of multiple tests with the Ca & Mg for the sole purpose of evaluating the variability I introduce with how I test. (That silly dropper bottle for Ca-2 is really hard to get consistent drops! LOL) There is certainly some variability there, but the biggest deviation was about 30 ppm in the Ca on one test. The others were essentially the same.

 

[shred5]

OK, it appears mixing/sampling is not the cause for your variation, but I was speaking more generally in that it should be considered. Also, the Ca and Mg look pretty high for IO, those look more like RC numbers, and that's where UPG saves some manufacturing cost - by adding less of these components, so perhaps they mislabled/mishandled a batch of RC for IO. Very unlikely but that's more likely than a batch making it past QC testing - though there are acceptable ranges for all parameters. Especially alk, that changes so quickly after you add water that I'd bet the acceptable range is fairly wide for most manufacturers. And again, if you're doing small water changes these differences don't mean squat (unless you're not dosing or keeping up with biotic and abiotic losses - eventually low numbers could catch up with you). Don't like the high alk? Aerate for a while or add some acid. The low Ca is the only real concern - though not sure how much above 1500 your Mg is, but I've had my Mg up to about 2000 during a bryopsis battle with no ill effects. I think there's a general consensus wrt success in reefkeeping, it's not the salt but nutrients and stability within normal seawater ranges. Not saying it's the case for you but I think lots of us (me especially) end up chasing the wrong "demons" - in my most recent case I was having a devil of a time with nitrate and things generally looking blech when I finally decided to cast out a large neon devil's hand leather coral I've had for 10 years and my system almost instantly turned around. But that's not to say your salt is not giving you issues, it's just IME it turns out to be something else - usually.

I agree with your first statement with settling in the bag, I was just stating it is not what is happening for me.
I use a dosing system on my tank so stability from batch to batch is important. It is also important that I change the exact same amount of saltwater or it throws my dosing off. I sometimes have to up the amount due to growth.

 

[Myka]

To it looks like your salinity measuring may be off as the testing batch with the highest calcium also has the highest alkalinity, and the batch with the lowest has the lowest alkalinity amd Mg. It appears to be a concentration issue. If you're only weighing it and not actually checking the salinity that could be the issue as the salt could have higher or lower humidity.

Do you calibrate your refractometer? Do you read it under the same light you calibrated with? Is it an ATC refractometer?