specific gravity problem

[SilviaGTO]

hi. Im trying to turn my freshwater tank into a brackish water tank suitable for green spotted puffers.
The pH and kH of the water are perfect but ive been having trouble with the salinity
at the moment i have no fish in the tank. ive been adding about a tablespoon of synthetic salt per gallon gradually (dont ask why, i know i dont have any fish). I have a 5 gallon aquarium with a penguin mini on it, and so far I have added about 3 tablespoons of salt to the aquarium.
I went to check the specific gravity of the water and i got.. 1.000
I had borrowed my mothers sg meter from her house, and its just a plastic one with a lever on it so i figured something was wrong with it. so I went and bought one of the hydrometers that float in the water.
its still reading 1.000 after i added a fourth tablespoon of salt today.
Can anyone tell me what is going on? is my penguin working too well and taking the salt out? I have normal stone gravel you buy from a pet store in my fish tank, i wouldnt imagine that had anything to do with it.
Anyone got any ideas?

 

[Anemoneman]

It takes 1/2 cup per gallon to get 1.023 (2.5 C in 5 gal). 1/2 C is 8 Tsp. You have added 4 tsp in 5 gallons. That's .25 C in 5 gallons. 10 times more dilute than seawater.

Try adding more salt.

 

[SilviaGTO]

thanks. i read somewhere that it was a tablespoon per gallon. guess they were wrong . thanks!

 

[fishfreek]

I think that might have been for medicimual use of salt in freshwater tanks. Using small amounts of salt in freshwater tanks can be benifical to the overall health of your fish. But its my understanding that brackish tanks should be up around 1.010 or something like that. So my guess i you would need to add close to 1 cup of salt before you would see any real swings in the SG.

 

[SilviaGTO]

Thanks! yes 1.010 is what I am aiming for. As soon as I started adding greater quantities of salt my hydrometer actually started giving me a reading.