Different salinity at different locations

[wood_stock]

I am having problems measuring my salinity of my tank. The readings are different when I collect the water from different locations, e.g. main tank, sump inlet and outlet. Other than the possibility of a faulty meter, are there any other explanations to this?

[Achilles Tang]

What kjind of equipment are you using for the testing?

[wood_stock]

just a simple Coral Life hydrometer.

[Achilles Tang]

The simple explanation could be that collecting water at the sump inlet and outlets will lead to a lot of microbubbles that cling on and affect the buoyancy of the floating needle.

Try tapping hard a few times to knock off any bubbles before taking a reading.

[wood_stock]

Ok, thanks. Maybe i'll try with another hydrometer too.