Salinity doesn't seem to rise

[Kial]

So my water level has been dropping significantly lately, I'm guessing its due to the heat were having and I'm using a cooling fan.
I read that once the water evaporated my Salinity would rise, but mine is staying the same?

Im using a refractometer and manually topping up water. Not got around to buying auto top off yet.

 

[Ludders]

Are you topping up the water as it evaporates or do you leave it to drop and then test the sg?

Sorry I am totally confused by this initial post.

 

[Crabs McJones]

So my water level has been dropping significantly lately, I'm guessing its due to the heat were having and I'm using a cooling fan.
I read that once the water evaporated my Salinity would rise, but mine is staying the same?

Im using a refractometer and manually topping up water. Not got around to buying auto top off yet.

If you're manually topping off water with freshwater your salinity won't change. If you let the tank go and didn't top off your salinity would start rising. But as long as you're topping off daily it'll stay relatively the same.

 

[Waters]

As others stated, your salinity will not change if you are adding fresh water back in. When salt water evaporates, the salt remains and only the fresh water is removed...which you are adding back in manually.

 

[Kial]

Sorry I should of said, I was not topping up daily as didn't notice it dropping.I checked it few days later and it dropped quite a bit. Saliniy was still the same? I'm topping up daily now but am just curious to why it didn't change

 

[nautical_nathaniel]

What size is your aquarium and what are you using to measure salinity with?

 

[SashimiTurtle]

The bigger the system, the less of a change you'll notice. You're corals will notice the change more than you will, especially the harder to keep SPS.

 

[Kial]

Tank is 400l and using refractometer.
I don't have any coral or fish yet, only a few snails

 

[Bradw18]

I personally would mix a batch way higher then normal and test it add double the salt to a gallon of water let it mix and test it. Do it before a water change so you can add another gallon of fresh water so the good saltwater dosnt go to waste. Atleast you'll know if there's a problem with your refractomoter

 

[Randy Holmes-Farley Verified Community Expert]

It definitely changed, you just didn't detect it.

If the tank is 18 inches tall (18 inches of water), and the level dropped one half inch, the salinity would rise by 0.5/18 = 0.028, or 2.8%.

That means 35 ppt would become 36 ppt, or a specific gravity of 1.0260 would become 1.0267.

 

[Kial]

Ive done that when I've mixed salt water before for my water changes. As I'm still getting used to how much I need to add I always need to adjust the salinity so I'm certain the refractometer is fine.

 

[Kial]

Ah OK I see. I suppose I was expecting the salinity to rise by a huge amount.

 

[Randy Holmes-Farley Verified Community Expert]

Always good to do math.

Happy Reefing!

 

[Kial]

Me and maths have never got on

 

[FishOfHex]

So my water level has been dropping significantly lately, I'm guessing its due to the heat were having and I'm using a cooling fan.
I read that once the water evaporated my Salinity would rise, but mine is staying the same?

Im using a refractometer and manually topping up water. Not got around to buying auto top off yet.

It would depend on how big your tank is before you notice an increase in salinity. Evaporate .5 gallon from a 30 gallon and a 300 gallon you would probably not see any difference in the 300

 

[Instigate]

Also your results will be different depending on the light source you're using to look through the refractometer with. Sunlight vs a cool blue led vs a daylight cfl all gave me different results so I calibrated with the cfl and only use it to test sg now.

 

[Kial]

Oh OK I definitely didn't know the light can give different readings. I'l have to just stick to one from now on.
Thanks for the replies everyone