JohnnyBlowfish
Active Member
For 5 gallons start with 3.5 cups of salt. That usually gets me really close to 1.026. However, you’ll likely find that weighing the salt mix will give you more consistency than a measuring cup.
Instant ocean salt
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just_matt
New Member
I learned and always used 1/2 cup per gallon, but that always ended up with me having to creep up on the right number, mix and test and add, mix and test and add, which is a pain, or overshooting and having to add water, which is also a pain (and sometimes not room in the bucket). After literal years of that hassle, it recently occurred to me to use a kitchen scale, and I've never looked back. I figured out I get good consistency with my last bucket of Reef Crystals at 155g/gallon on a decent kitchen scale (a nickel should weigh 5 grams exactly).
I only have a 32 gal cube, so 3.5 gal marking on my bucket makes for a good 10% water change. 3.5 gal ro/di * 155, exact amount works out to 542.5, I aim for that or a little over, 550-555, and I'll come out at right at 1.025. First couple times I added 155g at a time in multiple lifts, but lately I've just been dumping ~550g at once and letting the pump run.
Also knowing the actual mass of salt required lets you invert the math, which would useful if your mix (or your actual tank) is low. If you know that it's 155g/gal to go from ro/di 1.000 to 1.025, the inverse means it will take almost exactly the same amount to take 25 gallons of water from 1.024 to 1.025.
I only have a 32 gal cube, so 3.5 gal marking on my bucket makes for a good 10% water change. 3.5 gal ro/di * 155, exact amount works out to 542.5, I aim for that or a little over, 550-555, and I'll come out at right at 1.025. First couple times I added 155g at a time in multiple lifts, but lately I've just been dumping ~550g at once and letting the pump run.
Also knowing the actual mass of salt required lets you invert the math, which would useful if your mix (or your actual tank) is low. If you know that it's 155g/gal to go from ro/di 1.000 to 1.025, the inverse means it will take almost exactly the same amount to take 25 gallons of water from 1.024 to 1.025.
Last edited:
reefer2/19/24
New Member
I do 5 gallons at a time and use 21/2 cups and use a small heater and and a Fluval powerhead and mix over night and every time it comes out to 1025. IO reef crystals.
I have the exact same results with IO RC. 2.5 Cups to 5g is just below my desired 1.026 and I add a bit more to bring it up
I've been using IO for years and have never gotten 1.026 using 1/2c per gallon rodi. I mix in a brute and use 15 cups to get 1.025 in 28g rodi and occasionally will have to add a little more. Salinity measured with calibrated refractometer, Hanna, and TM hydrometer.
jerricolaboy
Community Member
Usually 2.5 cups for a 5 gallon water change gets me to 1.025 and I have to adjust a little sometimes here and there. Usually mixing with a heater and maxijet in the bucket for at minimum an hour before I check with refractometer. And I recalibrate my refractometer about once every month. Can’t be too cautious
MrPike
Active Member
Here are a couple “best practices” for using a refrac.
1.)Rinse the lense flap and the end of the unit in ro water before and after testing. The reason for this is if saltwater is allowed to evaporate, those salt crystals will dissolve again when you take your next sample.
2.) take multiple readings every time, like 10 readings. Don’t stop actually until you get some consistency.
3.) make sure the “flap” hasn’t rusted where it can’t sit cleanly on the lense, if it has, oil it or get a new one.
4.) make sure the unit is not freezing cold or boiling hot, like what would happen if it sat in a cold garage in winter or hot garage in summer.
5.) get a floating hydrometer to test against
6.) get a calibration solution meant only for refractometers, not ones that work for conductivity, they are slightly different.
I think that’s it, they are kind of a pain
1.)Rinse the lense flap and the end of the unit in ro water before and after testing. The reason for this is if saltwater is allowed to evaporate, those salt crystals will dissolve again when you take your next sample.
2.) take multiple readings every time, like 10 readings. Don’t stop actually until you get some consistency.
3.) make sure the “flap” hasn’t rusted where it can’t sit cleanly on the lense, if it has, oil it or get a new one.
4.) make sure the unit is not freezing cold or boiling hot, like what would happen if it sat in a cold garage in winter or hot garage in summer.
5.) get a floating hydrometer to test against
6.) get a calibration solution meant only for refractometers, not ones that work for conductivity, they are slightly different.
I think that’s it, they are kind of a pain
GARRIGA
2500 Club Member
West Palm Beach Reefer
305 Reef Club
MAC of SW Florida
Rock Pool Reef Keepers
Might be a stupid question but are you trimming the excess off the cup so it's exactly a cup measurement?
Having said that, I'm going to start weighting salt vs relying on how much salt contained within a cup. Might want to try that and see how it goes. I'd also get an old school hydrometer as a second check on the accuracy of that refractometer. Not saying this will be more accurate but if both similar then more likely the mix is wrong vs the results.
Having said that, I'm going to start weighting salt vs relying on how much salt contained within a cup. Might want to try that and see how it goes. I'd also get an old school hydrometer as a second check on the accuracy of that refractometer. Not saying this will be more accurate but if both similar then more likely the mix is wrong vs the results.
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Joel j
Community Member
Ok, so I bought 4 gallons of distilled water. Dumped in my bucket and made a mark. Bought measuring cups.
I test with a brs refractometer calibrated with the brs calibration solution. Have a 550g/hrs pump in the bucket to mix. At 1/2 cup to 4 gallons I get a reading of 43ppt. Idk how much the temp affects the reading but I am not heating the water. Mixing time makes no difference in the reading.
I belive I have to trust the refractometer. It reads 0ppt with the rodi water and 35ppt with the calibration solution.
Only got my tank about half full, takes for ever with a 50gpd rodi unit. Next 4 gallon I am going to start with a 1/4 cup and see where that gets me.
I test with a brs refractometer calibrated with the brs calibration solution. Have a 550g/hrs pump in the bucket to mix. At 1/2 cup to 4 gallons I get a reading of 43ppt. Idk how much the temp affects the reading but I am not heating the water. Mixing time makes no difference in the reading.
I belive I have to trust the refractometer. It reads 0ppt with the rodi water and 35ppt with the calibration solution.
Only got my tank about half full, takes for ever with a 50gpd rodi unit. Next 4 gallon I am going to start with a 1/4 cup and see where that gets me.
This. It is absolutely impossible for 1/2 cup of salt added to 4 gallons of water is getting 43ppt.
It’s either human error or faulty refractometer.
Get a Tropic Marin glass hydrometer and be done. You will never use a refractometer again after seeing how much easier and better the TM hydrometer is. Just be careful as they are glass and fragile.
My bathroom scale isn't that accurate?
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Joel j
Community Member
First I would like to thank everyone for there replies.
With all the replies stating that the 1/2 cup per gallon should be right, I decided it must be some kind of measurement error/testing error.
This is my conclusion. My rodi water has a tds of 5. I'm not concerned about that, it has always tested at 5ppm. The tds of the calibration solution should be 3500ppm. My tester does not read that high. I am only getting a tds off 250ppm on the calibration solution.
I calibrated the refractometer to zero with my rodi water. Put drops of calibration solution on it and it still reads zero.
Mixed 4 gallons of water 1/2 cup per gallon and test. Reads just shy of 35ppt.
So I'm guessing I have a bad calibration fluid. I also reversed the test also. Calibrated at 35ppt with the fluid and then tested rodi water. It read 35ppt!.
With all the replies stating that the 1/2 cup per gallon should be right, I decided it must be some kind of measurement error/testing error.
This is my conclusion. My rodi water has a tds of 5. I'm not concerned about that, it has always tested at 5ppm. The tds of the calibration solution should be 3500ppm. My tester does not read that high. I am only getting a tds off 250ppm on the calibration solution.
I calibrated the refractometer to zero with my rodi water. Put drops of calibration solution on it and it still reads zero.
Mixed 4 gallons of water 1/2 cup per gallon and test. Reads just shy of 35ppt.
So I'm guessing I have a bad calibration fluid. I also reversed the test also. Calibrated at 35ppt with the fluid and then tested rodi water. It read 35ppt!.
jimk60
Well-Known Member
Agreed with the TM hydrometer. With me refractometer calibration was nothing but trouble.
This is exactly what I do as well
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