Salinity - ppt vs S.G. (Need Help Knowing How To Properly Measure)

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JSkeleton

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Again... the point is irrelevant... weather you measure in cups or grams, the goal is 35 ppt. this is best achieved by adding salt, testing, and adjusting. Knowing if 4000g is the target is pointless... You may not have the same amount of water to start from, you may have leftover saltwater at the beginning. Its all based on repeated process and best estimate.
Right and true, but again, I’m not looking for an exact “put this many cups and every time it’ll be 35ppt” sort of thing, but more of a basis to at least start from. Like to learn if I put X=amount it’ll get me at least ballpark and then I can adjust from there sort of thing.
 

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Right and true, but again, I’m not looking for an exact “put this many cups and every time it’ll be 35ppt” sort of thing, but more of a basis to at least start from. Like to learn if I put X=amount it’ll get me at least ballpark and then I can adjust from there sort of thing.
OK.. The container my salt comes in says 1.4 cups per 5 gallons. If 1 cup is 290 grams than 1.4 cups is 406 grams.
 

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Oh boy, so for a 55g how often would you burn through say 5g in an ATO?

Also, would you happen to have a good ATO in mind to recommend? Upon a quick search the "AutoAqua Smart ATO Micro" seemed good but maybe not the best? My wallet is already hurting and to be fully honest I'm already partly regretting going saltwater and not just going freshwater again, but I'm this far now haha
You can do without if you are home, top up 3 times a day, before you go out, in the evening and before bed, yes an ATO is good to have, but they do come with issues, you just need your sock or floss to get clogged up with detritus, that Will slow the water flow down, triggering the ATO when it shouldn’t be going off, so as said if you can top off 3 times a day that would be fine u til you have the money and understand better how to keep your salinity stable…I top off manually, got sick of my ATO triggering by mistake.

Keeping your salinity stable is the key, 1.0264 is said to be the average salinity but all seas are not the same salinity so don’t get too hung up with hitting a certain number, as long as you aim for the same salinity each time, it doesn’t really matter what the number is as long as it’s close to the average.
 

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Again, add less and adjust as needed. it is far easier to add salt. For example, you have your mixing container mostly full with RODI water... you add salt based on a number and find you are WAYYY too salty... you can only add so much more water before you overfill the container right?

On the other side.. if you add some salt, test it and find its low, you can easily add more...
 

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I will be interested to follow you with you in a year or so.. after you have done this salt mixing thing a few dozen times... and you realize that the fear you have now is akin to a new parent. the baby spit the pacifier on the ground?? OMG boil it, bleach it, it MUST be sterile... after the 2nd or 3rd kid, you wipe it on your shirt and pop it back in the kids mouth... no worries.. lol
 

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Slightly off (but still on) topic...you mentioned mathematical calculations which got me thinking. 35ppt = 35g of salt per Liter of water, correct? How would I go about figuring how much salt to measure when mixing per gallon? Is there a certain equation or something? Everywhere I search goes by Grams for salt, but I (and I think a lot of people) go by Cups. Yet, I can't find any definitive answer on how many grams are in a cup, since grams are weight and cups is more of a measurement.
You cannot weigh out 35 g of salt because there is typically a large amount of moisture in the salts used, especially in the calcium and magnesium components which form specific crystals that hold water in them.
 

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Yes, 35g/L. Easiest way is to measure the weight of a full cup. I have a set of digital scales I use only for measuring salt. I use 2.1kg for my 60L drum.

Just to be clear, that won’t work to get to 35 ppt. The mass needed is well above 35 g/l.

if you figure out for a given brand what mass gets you to 35 ppt, you can do that, certainly, but it might change if the moisture level in the salt changes.
 

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Just to be clear, that won’t work to get to 35 ppt. The mass needed is well above 35 g/l.

if you figure out for a given brand what mass gets you to 35 ppt, you can do that, certainly, but it might change if the moisture level in the salt changes.
That's true, and will certainly be affected by how much moisture your salt has been exposed to (e.g. keeping it stored in a sealed bucket vs a cardboard box). I've had no issues using this as a basis for mixing 60L of water at a time. I just check it once it's had a day circulating and adjust if necessary.
 

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That's true, and will certainly be affected by how much moisture your salt has been exposed to (e.g. keeping it stored in a sealed bucket vs a cardboard box). I've had no issues using this as a basis for mixing 60L of water at a time. I just check it once it's had a day circulating and adjust if necessary.

But right out if an unopened box it also will not be 35 g/L unless it is specifically made with anhydrous ingredients, which is not the norm.
 

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But right out if an unopened box it also will not be 35 g/L unless it is specifically made with anhydrous ingredients, which is not the norm.
I already agreed and added that it will be further affected by exposure to moisture. I would still use this as a starting point. I'm not weighing out 60kg of water, just using a molded line in a drum. I'm going to have a margin of error and without knowing the specifics of the hydrous ingredients, all I really know is that I won't be adding too much salt to my mixture as a starting point.
 

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So I got a Hanna Salinity Tester which by default is in ppt and the calibration packets are by ppt but can also measure by S.G..

Now, I heard that ppt is a more accurate measurement (correct me if I'm wrong) since it's based solely on salt, while S.G. factors in temperature (which gets confusing for me to be quite honest). So I was happy just going by ppt.

BUT...Every time I try to get info on best salinity for certain livestock, it's ALWAYS giving the salinity readings in S.G. and so I'm left scratching my head. So what should I do?
Technically PSU is the measure you should using if you're measuring using a conductivity meter.

Practically, it probably doesn't matter as long as you keep it consistent.

Just aim for 34.8 PSU or round up to 35.
 
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You can do without if you are home, top up 3 times a day, before you go out, in the evening and before bed, yes an ATO is good to have, but they do come with issues, you just need your sock or floss to get clogged up with detritus, that Will slow the water flow down, triggering the ATO when it shouldn’t be going off, so as said if you can top off 3 times a day that would be fine u til you have the money and understand better how to keep your salinity stable…I top off manually, got sick of my ATO triggering by mistake.

Keeping your salinity stable is the key, 1.0264 is said to be the average salinity but all seas are not the same salinity so don’t get too hung up with hitting a certain number, as long as you aim for the same salinity each time, it doesn’t really matter what the number is as long as it’s close to the average.
3 times a day!? Surely water doesn't evaporate THAT fast, does it?? And are ATOs that unreliable and finicky? Are there not some that have some kind of security mechanism to avoid triggering by mistake or is it that common?
 
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I will be interested to follow you with you in a year or so.. after you have done this salt mixing thing a few dozen times... and you realize that the fear you have now is akin to a new parent. the baby spit the pacifier on the ground?? OMG boil it, bleach it, it MUST be sterile... after the 2nd or 3rd kid, you wipe it on your shirt and pop it back in the kids mouth... no worries.. lol
Haha that is a good point! I'm also curious where I'll be with it all in a year or so! I guess that's part of the beauty of the hobby, right?
 
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Technically PSU is the measure you should using if you're measuring using a conductivity meter.

Practically, it probably doesn't matter as long as you keep it consistent.

Just aim for 34.8 PSU or round up to 35.
Is PSU and PPT not very closely the same essentially? For example, 35ppt seems to be 35PSU (at least roughly) no?
 

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3 times a day!? Surely water doesn't evaporate THAT fast, does it?? And are ATOs that unreliable and finicky? Are there not some that have some kind of security mechanism to avoid triggering by mistake or is it that common?
Yes, depending on the size, my tank is only very small but it needs around 500ml a day, some need many litres a day.
Yes they can be finicky, triggering for unknown reasons, flow is a big issue, if it changes for any reason such as a snail passing over the overflow or floss getting dirty that can slow the flow, triggering the ATO, yes some have more safe guards than others but they all can have their issues.
 

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3 times a day!? Surely water doesn't evaporate THAT fast, does it?? And are ATOs that unreliable and finicky? Are there not some that have some kind of security mechanism to avoid triggering by mistake or is it that common?
I apologize if I missed any info you posted about tank size/age and livestock but I'm making the assumption that your tank is pretty new and you only have a couple of fish (no difficult corals).

It's tempting to want to figure out and solve EVERYTHING right out of the gate -- maybe don't do that. (Focus on basics in the beginning)

Without really knowing anything for sure, I'm tempted to suggest this:
-- Just top off manually for now, daily. (If you're home you can check and top off multiple times but I'd say daily is fine)
-- Maybe shoot for 34 ppt and just do the best you can for now. (Don't test throughout the day and freak out at minor variances and do anything about it -- just top off so your water level stays consistent)
-- You'll figure it out and once you do, if/when you find manual top off is becoming a nuisance, then start researching ATO systems and containers.

*just my 2 cents -- oh,,, sorry,,, you're in Canada,,, not sure what the monetary conversion is,,, just kidding
 

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Is PSU and PPT not very closely the same essentially? For example, 35ppt seems to be 35PSU (at least roughly) no?
They are close.

PSU is a technical standard designed for measurement of conductivity whereas PPT is a measure of the weight of disolved salts.

If your measurement instrument gives you a choice I'd go for the PSU standard.

I know that Hanna let you choose, and the GHL profilux defaults to PSU.

 

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3 times a day!? Surely water doesn't evaporate THAT fast, does it?? And are ATOs that unreliable and finicky? Are there not some that have some kind of security mechanism to avoid triggering by mistake or is it that common?
Many/most ATO have some kind of failsafe built in but it still isn’t unheard of for them to fail. Having an ATO stay on when it shouldn’t can potentially be catastrophic for the tank and your house depending on how much water it can pump into your tank from the reservoir.

As for evaporation I evaporate about 1.5g a day from my roughly 100g tank and about 2g from my 125g tank. There are a lot of factors that effect evaporation rates including amount of surface agitation, type of covers on the tank, your ambient humidity, etc.

The more times you manually top off the tank the better but I would think that once a day should be the minimum. If you don’t want to buy an ATO right now you can figure out how much water you need to add and setup a dosing pump to add that much daily. I don’t know how much cheaper it would be than a ATO though. That is how I keep salinity in my qt tank stable.
 
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I apologize if I missed any info you posted about tank size/age and livestock but I'm making the assumption that your tank is pretty new and you only have a couple of fish (no difficult corals).

It's tempting to want to figure out and solve EVERYTHING right out of the gate -- maybe don't do that. (Focus on basics in the beginning)

Without really knowing anything for sure, I'm tempted to suggest this:
-- Just top off manually for now, daily. (If you're home you can check and top off multiple times but I'd say daily is fine)
-- Maybe shoot for 34 ppt and just do the best you can for now. (Don't test throughout the day and freak out at minor variances and do anything about it -- just top off so your water level stays consistent)
-- You'll figure it out and once you do, if/when you find manual top off is becoming a nuisance, then start researching ATO systems and containers.

*just my 2 cents -- oh,,, sorry,,, you're in Canada,,, not sure what the monetary conversion is,,, just kidding
Thanks for the response!

My tank is new, yeah! No fish yet. Did a fishless cycle and my ammonia finally 0’d out a couple days ago, but Nitrites are still like 2.0 so not sure what to do haha Put a few drops of Dr Tim’s ammonia couple times but not sure if enough (to avoid starving bacteria).

But yeah, I definitely want to at least get things stable (the basics at least) for now! Planning to start with 2 clowns and a Cuc of Skunk Shrimp, Trochus + Nassarius Snails :)
 
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