how to balance sg formula

[junk]

Is there a site or formula that will help you figure out how much water to add with one sg to bring your existing water to the level you want?

For example, when away I came home to a tank at 1.027 (I normally try to stay at 1.024). If it's a 120g, with roughly 25g in the sump and 20g in the fuge, how much do I need to swap out with 1.020 water to bring it back to 1.024?

thx

 

[Mbodell]

I don't know, but I would add an autotop off so you don't have to worry about things like that.

 

[Phyl]

You would need to do a 40% water change at 1.020. If you used fresh water you would only need a 10% change.

Here's the formula that I used:

((165g*.9*1.027)+(165*.1*1))/165 = 1.0243

((165g*.6*1.027)+(165*.4*1.020))/165 = 1.0242

I plugged it into excel and changed parameters until I got the results you were looking for.

 

[junk]

Thanks Phyl.

I'll do a 10% change with fresh RO/DI water first, then wait a day and do my reg change with 1.024 then. Thanks.