lowering salinity question

[GaryL]

ok so my salinity is up to 1.030 not sure how it got there but...i am slowly lowering it....

 

here is the question...if my tank is a 150 + 15g in the sump...how many gallons would it take of FW to lower to 1.025? and is there an equation to attain said number?

[Freezerburn]

Not sure I just kinda eyeball/winged it. when something like that happens, maybe dump 5 gallons and put 5 gallons of RO in. maybe in 1 gallon increments testing the water after it's had time to mix up. if it didn't do enough rinse and repeat.

[txaggies07]

I am pretty sure salinity is linear. Thus, you would need to replace 27 gallons of 1.030 with fresh water to lower to 1.025.

[davelin315]

1.030 = 39.8 ppt

1.025 = 33.2 ppt

165 gallons

6567 (1.030)

5478 (1.025)

Need to reduce overall concentration by 1089 parts of salt

27.36 gallons of fresh (6567 - 1089 = x ; x * 165 = 27.36)

137.64 gallons of 1.030 need to remain

So, based on those calculations, I come up with the same thing, 27.36 gallons of fresh water needed...

 

I am positive that there's probably an easier way to do it, but I haven't done any complicated math in a long time!

[wreck]

yeah, what he said..

 

Are you using a refractometer? Just be sure your measurement is correct.

[JMsAquarium]

 

I am positive that there's probably an easier way to do it, but I haven't done any complicated math in a long time!

 

Absolutely, there is an easier way. Of course your calculations are correct. Now, as usual, nothing good happens fast. I'd drip RODI slowly, until reaching the targeted lower salinity.

[GaryL]

I am pretty sure salinity is linear. Thus, you would need to replace 27 gallons of 1.030 with fresh water to lower to 1.025.

 

awesome!

 

 

1.030 = 39.8 ppt

1.025 = 33.2 ppt

165 gallons

6567 (1.030)

5478 (1.025)

Need to reduce overall concentration by 1089 parts of salt

27.36 gallons of fresh (6567 - 1089 = x ; x * 165 = 27.36)

137.64 gallons of 1.030 need to remain

So, based on those calculations, I come up with the same thing, 27.36 gallons of fresh water needed...

 

I am positive that there's probably an easier way to do it, but I haven't done any complicated math in a long time!

 

thanks....just what i was looking for. kinda in shorthand instead of reading a paper someone wrote

 

 

yeah, what he said..

 

Are you using a refractometer? Just be sure your measurement is correct.

 

yes i am....wouldnt dream of using anything else

 

 

Absolutely, there is an easier way. Of course your calculations are correct. Now, as usual, nothing good happens fast. I'd drip RODI slowly, until reaching the targeted lower salinity.

 

working on it but gotta figure in the top off too

 

 

thanks so much ... i may have more questions....i'm the guy who isnt afraid to look like a dummy to ask questions

[YBeNormal]

You're going to replace 27 gallons of saltware with 27 gallons of RO/DI all at once so the math won't be quite that simple. The salinity didn't rise overnight though, so there should be no reason to lower it quickly either. Here's what I'd suggest:

 

Remove a gallon of tank water twice per day for the next thirteen days and let your ATO replace it (and water normally lost to evaporation). Measure salinity after thirteen days and continue the process until you've reached your target salinity. This will give you a gradual and safe reduction of salinity with very little effort.

[txaggies07]

1.030 = 39.8 ppt

1.025 = 33.2 ppt

165 gallons

6567 (1.030)

5478 (1.025)

Need to reduce

Edited July 16, 2008 by txaggies07

[tygger]

You're going to replace 27 gallons of saltware with 27 gallons of RO/DI all at once so the math won't be quite that simple. The salinity didn't rise overnight though, so there should be no reason to lower it quickly either. Here's what I'd suggest:

 

Remove a gallon of tank water twice per day for the next thirteen days and let your ATO replace it (and water normally lost to evaporation). Measure salinity after thirteen days and continue the process until you've reached your target salinity. This will give you a gradual and safe reduction of salinity with very little effort.

 

Exactly...

 

I wouldn't try to get it to 1.025 overnight so it's going to take more than 27 gallons total if you're only replacing a few gallons at a time.