Is there something wrong???

[DeadOrAlive]

Hi,i am currently using dymax glass hydrometer which is a hydrometer which bobs in the water. When i did a partial water change 2 days ago,i checked the salinity level and it was fine but when i checked it today,the salinity level has dropped! I don't know whats wrong because i had placed a marker to indicate my water level when i did the pwc and the water level currently is below that marker so the salinity should be higher but mine is dropping. Is there something wrong with my hydrometer or what???

 

[melosu58]

Hydrometers are so unreliable. Get a refractometer.

Saltwater Aquarium Salinity & Specific Gravity Testing: Portable Refractometer

 

[Kurt_Nelson]

Actually... the floating glass hydrometers are pretty darn good, assuming you compensate for the temperature using the little chart that comes with them.

Did you check the salinity of the partial water change water before you added it to the tank? Was it the same as the tank? If you took the reading immediately after the water change, perhaps the new water hadn't had time to mix with the old yet? And your new water was lower in salinity than your tank?

How much of a drop are we talking about?