Salts Vs amounts = dilutions ?

[Saveafish]

Its pretty easy we all know by weight and by measurements how much salt to add to a gallon of water. By knowing this we get our .026 sg.
Here is my question. Is there a backwards table for adding water to a gallon amount to bring it down by.
Example.
If I have 1000 gallons. How many gallons does it take to bring it down from .026- .025?

 

[Tastee]

It is just the reverse. You are removing SW before adding in FW to reduce your salinity. FW has no salt. So you just need to calculate how much SW to remove.

Let’s take my QT as an example. Sorry, I am from ‘down under’ so this is metric. I drop salinity back to 1.020 (28.6 ppt @ 25 degrees C) from 1.026 (36.5 ppt) after I introduce a fish to the DT before I put a new fish into QT.

My QT is 35 litres. I need 3.8 Kg of Aquaforest salt per 100 litres to get to 33 ppt. This means ~1.5 Kg salt in 35L to get to 36.5 ppt. That is ~40g/ppt, and ~42g/litre. If I want to drop 7.9 ppt to get down to 28.6 ppt I need to remove ~316g salt, or ~7.5 litres of water.

When lowering and raising I do the above, test my salinity and adjust up or down as needed to allow for variation in the salt etc. To raise I simply fill my QT’s ATO with SW until I reach the salinity I want, again I know roughly how much salt I need to add to the ATO to reach my desired level.