Ok i know this is a stupid question....but. when i go to do a water change, and start to pour my new water in, even if the water is the exact same SG than the tank water, my SG goes up drastically and i have to rush around to find some freshwater to add to the tank. I havent been topping off before i do water changes, but if both the SG of the tank and the SG of the new water are the exact same, shouldnt they STAY the same instead of making the tank water rise?

-adam

How are you measuring SG? If the SG in both water sources is identical then it shouldnt change when they are mixed.

You don't have salt creep inside your tank do you? If there is saltcreep above the water line, when you add new water and it touches the saltcreep it will raise the ending salinity.

Are you using a powerhead to stir the new water?

yes yes and no....yes im using a pwrhead, no i dont have any salt creep (surprisingly enough). But its the strangest thing. I dont understand it. Im not topping off before a water change, but if they are exactly alike, even if your displacing saltwater that has evaporated with saltwater freshly mixed, shouldnt it still stay at the same SG?

Im measuring with a refractometer. it has been calibrated recently as well.

How long are you mixing the SW for?

Try taking a reading after everything has calmed down, or try mixing the new saltwater for longer. It seems like it usually reads a much higher salinity for a while right after I add the salt, and eventually levels itself out. Of course, i've got a hydrometer.... no refractometer :/ I dunno if that would make a difference.

Also, are you raising the new water up to the same temp as the tank water before adding it? That'll mess it up too.

Also, are you raising the new water up to the same temp as the tank water before adding it? That'll mess it up too.


A lot of the refractometers now-a-days have automatic temperature compensation.

i dont heat my water before adding it because my tank is pretty much at or near room temperature, and since i do small water changes more often, i was told this wasnt necessary.

If it was my refrac that you were referring to...no it automatically compensates for temperature. Or at least thats what the manufacturer claims.

I'm alittle confused by these statements

But its the strangest thing. I dont understand it. Im not topping off before a water change,

and

even if your displacing saltwater that has evaporated with saltwater freshly mixed,

If you're not topping off before a water change then the SG would likely be higher in the display, and would slowly increase over time, but you've stated that the SG is the same in both water sources.

I'm assuming that your testing the SG of both water sources prior to a water change, is this true? Why not top off prior to a water change? How much is a drastic change in SG?