liter calculator

[Marcel2586]

Hi,

I have a aquarium of 260 liters.
Once in a while i need to refresh 20 to 40% of the water.

I have in excel a height width and depth cell and a cell with the calculation =B3*C3*D3/1000

I now want to calculate the height minus 20% of water, so i can mask-tape it and tap the water. i know, why bother and drain it on feeling, but hey, i have a computer!
How can i calculate this. i was thinking calculate liters minus 20%.
Depth and width do not change. and then calculate again to get the height.
Can someone help me please?

Thanks in advance.

 

[RainLover]

To reduce volume by 20% reduce the height by 20%

 

[Marcel2586]

Ehhhhhh, so simple (hit myself on the head) many thanks.

 

[RainLover]

You get days like that.