How many gAllons is 20% for 75 gallon water

[Daylilly]

Just wondering for a water change
I want to do. 20% water change for my 75 gallon tank

Thanks

 

[mfdrookie516]

75x.20=15.. granted, you probably have less than 75 gallons when you take in to consideration your substrate, rock, etc... but 15 gallons is going to be roughly 20%

 

[Gti_Leo]

15
10% is 7.5x2=15gallons of parcial water change