Low Tank Parameters - IO Salt

therealraf02 · May 16, 2025

Red_Beard said:
Oh yeah, just adding a pint simplifies that dramatically. You could even grab a before and measure again after it evaporates down and know precisely how much a pint adds for future calculations. Easily repeatable and you dont have to think about how much water you can change with the water you have mixed up.
The TM hydrometers are awesome. That is what i use too.

Added 1pt to the tank, which is currently at 1.0256. Will check back and see how much that raised it!

Randy Holmes-Farley · May 17, 2025

therealraf02 said:
Added 1pt to the tank, which is currently at 1.0256. Will check back and see how much that raised it!

Here’s the easy math. If you top off the tank for evaporation, then salinity rises.

If you add 1% of the tank volume, the salinity rises by 1%. (35 ppt to 35.35).

In sg terms, multiple the numbers besides the 1 by 1.01. So 1.02500 becomes 1.02525.

Red_Beard · May 17, 2025

Randy Holmes-Farley said:
Here’s the easy math. If you top off the tank for evaporation, then salinity rises.

If you add 1% of the tank volume, the salinity rises by 1%. (35 ppt to 35.35).

In sg terms, multiple the numbers besides the 1 by 1.01. So 1.02500 becomes 1.02525.

Randy, please pardon the aside from the question at hand, but how theoretically viable would it be to extrapolate total tank volume based upon given known tank salinity before and after the addition of a known volume with a known salinity? I know precision of the salinity measuring device would need to be quite accurate and precise and would likely be the limiting factor. Your thoughts sir?

therealraf02 · May 17, 2025

Red_Beard said:
Randy, please pardon the aside from the question at hand, but how theoretically viable would it be to extrapolate total tank volume based upon given known tank salinity before and after the addition of a known volume with a known salinity? I know precision of the salinity measuring device would need to be quite accurate and precise and would likely be the limiting factor. Your thoughts sir?

I’m wondering that too! I have no clue how many pounds of rock i have nor do I know how much water… lol

Randy Holmes-Farley · May 17, 2025

My expectation is its not better than an eyeball guess.

It depends on how precisely you can measure salinity, but let's look.

Suppose the tank volume is actually 100 gallons and is exactly 35 ppt (sg = 1.0264)

If you add 2 gallons of RO/DI, the salinity becomes 34.31 and the sg is 1.02588.

That change is a sg difference of 0.00052

How well can you reliably measure salinity?

Suppose it is very good and can distinguish 1.0250 from 1.0251. That difference of 0.0001 is 1/5th of the total. So the relative error is about 20%. 100 gallons +/- 20 gallons.

I think that is a correct analysis, but if anyone sees a problem, be sure to note it here.

Red_Beard · May 17, 2025

Randy Holmes-Farley said:
My expectation is its not better than an eyeball guess.

It depends on how precisely you can measure salinity, but let's look.

Suppose the tank volume is actually 100 gallons and is exactly 35 ppt (sg = 1.0264)

If you add 2 gallons of RO/DI, the salinity becomes 34.31 and the sg is 1.02588.

That change is a sg difference of 0.00052

How well can you reliably measure salinity?

Suppose it is very good and can distinguish 1.0250 from 1.0251. That difference of 0.0001 is 1/5th of the total. So the relative error is about 20%. 100 gallons +/- 20 gallons.

I think that is a correct analysis, but if anyone sees a problem, be sure to note it here.

Lol. Yep. 20% volume correction for a yield that is well within the margin of error of all hobby grade tools is not going to be of much practical use. Thank you for breaking that down for us!