Store bought saltwater 40ppt

[CornishCrustyCorals]

Hi guys I buy all my water premixed but today when I got it home I tested it as I always do before adding to my tank and it came up at 40ppt. I checked my tank and its sitting at 34.5.
I recalibrated my tester and got the same results. So I haven't added the water obviously. I have 3 x 5 gallon containers of the 40ppt.
I was wondering if anyone knows how much RO water I would need to bring 5 gallons of 40ppt down to 35ppt?

 

[NeonRabbit221B]

Google salinity calculator. Also fall your LFS and let them know

 

[CornishCrustyCorals]

Yeah I've let them know they're checking there batch they made up just waiting on call back but I have RO here and if I can reduce it down I can still do a water change.

 

[hds4216]

It should be about .7 gal RO per 5 gal 40 ppt water.

 

[CornishCrustyCorals]

23 x 0.040 = 0.92kg
23 x 0.035 = 0.805kg

So around 110g of salt per 23 ltrs
0.115 ÷ 0.035 = 3.28ltrs

Does this look right? I guess that is around .7g

 

[Cory]

Id check the calcium alk and magnesium to see if it correlates with 40ppt. Iirc mag should be 1400 and up at 40ppt for most salt mixes.

 

[CornishCrustyCorals]

I got it down to 35 and added to the tank now.

My mag is a little high 1650
Calc is 500

 

[Cory]

I got it down to 35 and added to the tank now.

My mag is a little high 1650
Calc is 500

Ask them what kind of salt they use maybe?