Salinity adjustment... math help. :)

[Jesse Sunday]

Short question...

I have a 32g tank that's at 33ppt, and I have 5g of new water at 39ppt. Is replacing 5g of the 32g with the new water OK?

I feel like I'm back in school with math word problems. :)

Long story...

My Instant Ocean Sea Salt mix that I've used for the past five months is good, I think... I've always had low Ca, etc.... so I'm changing to Red Sea Fish Pharm ARE11220 Coral Pro and want to up my (low?) salinity and also benefit from the added Ca / Mg / KH that I think the Instant Ocean Sea Salt doesn't have.

Thanks for any help given!

Jesse

 

[Mr. Mojo Rising]

thats a bit complicated, and I would not want to change my water with such drastic salinity difference. I would just do a normal water change, and then let the water evaporate to the salinity I want. That way its nice and slow.

 

[aSaltyKlown]

Top off the tank with 35ppt instead of RODI and gradually raise it over a few days.

 

[EricR]

Should give you roughly 34 ppt but don't think you want to do that much of a rise all at once.

I went with:
(27*33 + 5*39) / 32 = 33.9xxx

EDIT -- I agree to top off with saltwater to raise salinity gradually as the solution