Water evaporation

[Hooked on Corals]

Hello, I have a 250 gallon aquarium with a sump. And I’m losing about 5 gallons a day due to evaporation however, my salinity is not going down. It’s staying the same that’s with the evaporation of the freshwater. Why is my salinity not going down and what am I doing wrong?

 

[EnterName]

I'm not sure I'm understanding your question correctly.

Salt doesn't evaporate. Your salinity increases until you top off the evaporated water. That's why you are supposed to top off with freshwater.

Salinity is usually very stable in a tank. You are only losing salt when the skimmer is removing water from the system, but this is a very slow process and usually negligible. The amount of alkalinity and calcium you will need to add daily sooner or later will actually increase salinity faster than the skimmer can remove salt. This means there will come a point at which you will need to replace some tank water with freshwater to bring the salinity back down.

 

[Boehmtown]

Your tanks huge. It takes more than a day to get a reading to change much, if at all. Also make sure there isn't a tiny leak somewhere that you're attributing to evaporation , 5 gallons seems high. But I don't know your tank conditions etc

 

[Boehmtown]

Hello, I have a 250 gallon aquarium with a sump. And I’m losing about 5 gallons a day due to evaporation however, my salinity is not going down. It’s staying the same that’s with the evaporation of the freshwater. Why is my salinity not going down and what am I doing wrong?

Also your salinity would increase as pure(ish) H20 evaporates out of the system

 

[Ernie Mccracken]

If you start with 35.0ppt in 250 gallons of water and it evaporates 5 gallons, your salinity rises to 35.7ppt.

 

[Randy Holmes-Farley Verified Community Expert]

You probably just cannot accurately detect the change correctly noted above.

 

[Hooked on Corals]

So my freshwater is evaporating but the salinity isn’t going up. I’m adding back about 5g of freshwater back every day

 

[Dan_P]

So my freshwater is evaporating but the salinity isn’t going up. I’m adding back about 5g of freshwater back every day

When you replace the evaporated water with freshwater, your system’s salinity returns to the value before the evaporation occurred.

 

[Hooked on Corals]

So my freshwater is evaporating but the salinity isn’t going up. I’m adding back about 5g of freshwater back every day

When you replace the evaporated water with freshwater, your system’s salinity returns to the value before the evaporation occurred.

Ya I know but before I replenish the fresh water the salinity isn’t increasing

 

[Mr. Mojo Rising]

My ATO would need to be off for 2-3 days before it registers on the salinity tester. 5 gallons of 250 is only 2%. Leave the ATO off for a few days and you will see it increase.

 

[Dan_P]

Ya I know but before I replenish the fresh water the salinity isn’t increasing

Oh sorry. I think it is the answer above. The device you are using to measure salinity is not detecting the small salinity change caused by evaporating 5 gallons.

 

[Randy Holmes-Farley Verified Community Expert]

Oh sorry. I think it is the answer above. The device you are using to measure salinity is not detecting the small salinity change caused by evaporating 5 gallons.

Yes. There is not any possibility that water can evaporate without salinity increasing unless fresh water is being added back.

 

[Hooked on Corals]

Oh sorry. I think it is the answer above. The device you are using to measure salinity is not detecting the small salinity change caused by evaporating 5 gallons.

Yes. There is not any possibility that water can evaporate without salinity increasing unless fresh water is being added back.

I am using a refractometer and a hydrometer

 

[Dan_P]

I am using a refractometer and a hydrometer

These devices might not be able to detect small changes, just not sensitive enough.

 

[Randy Holmes-Farley Verified Community Expert]

I am using a refractometer and a hydrometer

Well, they are just not precise and accurate enough to see the difference. :)

 

[Hooked on Corals]

I am using a refractometer and a hydrometer

These devices might not be able to detect small changes, just not sensitive enough.

Okay thank you

 

[winxp_man]

As others have stated, 5 gallons is too minuscule for 250 system. Also the amount evaporating depends on so many factors that I don’t see here. Room/location temp, temp the tank is kept at, if fans are being used and so on.

My 340g system is in the garage, temp as of now is about 70 evenings/night and 82 during day. I’m using about 2.5 gals a day on average. Also pay attention to salt creep if you have any.