modifying salinity

[Planeden]

I made up 5 gallons of salt water last night and the salinity came out 1.027 (higher than I want). I figure there is a nice math-like way to adjust it so i went to the google. i found this, that i thought may be helpful to people. not what i wanted, but it calculates water change rates to adjust the salinty of your tank in increments.

http://www.hamzasreef.com/Contents/Calculators/TargetSalinity.php

for my purposes, i'm going to see if my logic works. i have water at 39 ppt and want it at 35 ppt. makes sense to me that i'll need to add:

39 ppt / 35 ppt * 5 gal - 5 gal = 0.6 gal of fresh water

unfortunatly, i have 5 gal in a 5 gal bucket, so, i have to test it later when i have more time to pour it around.

for the record, using the same ratio with the specific gravity does not work (1.027 to 1.022). i don't know why, but it may have something to due with the units of the specific gravity. i think SG is a relative density compared to that of water, so i don't think you can ratio a ratio. you'd have to convert the ratio back into a number with real units then ratio those.

[victoly]

coudnt you remove x amount of water and replace with fresh RODI?

[Planeden]

it amounts to the same thing. but that's what i am likely going to do. probably pull out 1/2 - 3/4 gal and fix that one to test my math. then i should have enough to fix the bigger container. i was just trying to figure a way to do it other than trial and error. that could take hours.

i'm still not sure why it is so salty. i used the same ammount of salt that i did the first time with this new salt, but got readings way higher.

[(Bio)³]

it amounts to the same thing.  but that's what i am likely going to do.  probably pull out 1/2 - 3/4 gal and fix that one to test my math.  then i should have enough to fix the bigger container.  i was just trying to figure a way to do it other than trial and error.  that could take hours. 

 

i'm still not sure why it is so salty. i used the same ammount of salt that i did the first time with this new salt, but got readings way higher. 

Compensate for temp?

Sent from my Samsung Galaxy S4

[Planeden]

it amounts to the same thing. but that's what i am likely going to do. probably pull out 1/2 - 3/4 gal and fix that one to test my math. then i should have enough to fix the bigger container. i was just trying to figure a way to do it other than trial and error. that could take hours.

i'm still not sure why it is so salty. i used the same ammount of salt that i did the first time with this new salt, but got readings way higher.

Compensate for temp?

Sent from my Samsung Galaxy S4

that is supposed to be "automatic". but by that, it may mean that the water and refractometer need to be close to the same temp. i know that when i used to keep my refract. in my cabinet and the fuge lights were on (gets warm) my salinity would be off by a ton. measured 1.032 in my tank once and 1.07 for RODI.

so, out of lack of understanding, i keep the tool at room temp and hope it knows what it's doing.

[Planeden]

let me ammend - when i got the high readings on the tank with the hot tool, i recalibrated it to 0. the next day i measured again and it was off by around 0.007, so i calibrated again.

[etschoerner]

Run the calculations at 4.5 gallons and see what the amount of RODI water should be added.

[etschoerner]

You are asking for a 12% increase in fresh water. Add that 12% to what you already have and cross multiply. 5/112= 4.46/100. So 4.46 should be the amount of saltwater you would have before adding fresh.

I think

[Planeden]

You are asking for a 12% increase in fresh water. Add that 12% to what you already have and cross multiply. 5/112= 4.46/100. So 4.46 should be the amount of saltwater you would have before adding fresh. I think

That is exactly backwards of the way I was thinking about, but the answer seems to be the same. So, if we both think it's right...

Not off work yet so haven't gotten around to trying it.

Thanks for the input.