How much freshwater in saltwater?

[mario]

The water I buy from the LFS is always 1.030 salinity.
How much freshwater (RO) should I add to 5 gals at 1.030 to lower the salinity to 1.025?
Is there a formula?

 

[sly]

I'm guessing you don't have a hydrometer... If you did then you should just add a little water at a time and mix it, measuring the specific gravity while you do it. Just add enough water to bring the SG down to where you want it.
You will probably add a little over a quart to get it to lower to that level. I just don't know of any formula.

 

[mario]

That's how I found out the salinity of the water from the LFS was soooo high.
I guess I'm gonna have to figure out the amount by slowly adding freshwater until the right salinity is reached, I was just wondering if a formula does exist

 

[pallan]

calibrate your refractometer to and maybe let the LFS know the diffrence as well they might not realize what they have. most LFS i know keep their salt lower than normal ive been told its easier on the fish. but i dont know if thats true. i suspect its to help combat ICH instead

 

[jerthunter]

I am not sure if specific gravity behaves like a concentration but if you want to test and see use the formular M1 * V1 = M2 * V2. Or in terms of this Final volume=(1.030)* Volume of water from LFS/(1.025) . I don't know if this will work with specific gravity but if you want to try it let me know if it works...

 

[winstew]

it will work. The relationship is linear. 5 gallons at 1.000 and 5 gallons at 1.050 will make 10 gallons of 1.025.

 

[moby]

Hey winstew and jerthunter, just thought I would throw this out there for discussion.
it will work. The relationship is linear. 5 gallons at 1.000 and 5 gallons at 1.050 will make 10 gallons of 1.025.
What about the temperature factor? That of course effects the salinity, so if 5gal is 1.000 at 50 degrees and 5 gal is 1.050 at 75 degrees and they are mixed, what then? :thinking:
Moby

 

[winstew]

well if you use a ATC refractometer then it will be fine. Temp doesn;t matter. Of course a hydormeter would give you diff result. Sorry should have clearned that up.

 

[bang guy]

Originally Posted by mario
The water I buy from the LFS is always 1.030 salinity.
How much freshwater (RO) should I add to 5 gals at 1.030 to lower the salinity to 1.025?
Is there a formula?
What was the temperature of the water when it tested 1.030?

 

[moby]

well if you use a ATC refractometer then it will be fine. Temp doesn;t matter. Of course a hydormeter would give you diff result. Sorry should have clearned that up.
This was sorta what I was getting at.
Mario, I assume that since the LFS provides your water, you are more that likely using an old fashion hydrometer. Correct? If that is the case, your test may not be accurate due to water temperature. If that is the case the salinity may be correct but you would get a false reading and may be diluting properly prepaired water.
It is possible the LFS may mix their water that strong but not probable, unless they have inexperienced staff members doing it.(what are the chances?!?!)

Moby