Water changes--real vs nominal tank volume

[The Kapenta Kid]

A, say, 10g nano holds a lot less than 10g water because of the volume taken up by sand, rock, and any internal equipment.
When you are calculating regular water changes do you base the percentage on the nominal volume (10g) or the real quantity of water in the tank plus whatever is in the sump or refugium?

 

[drty811]

i have always just calculated from the nominal volume, which just ends up being a larger percentage of a water change. dont think it really matters as long as you do them on a regular basis. i know ppl that do up to 50%, and as low as 5%. it all depends on what you keep, how much you feed, and your filteration. HTH

 

[skipm]

I now of a very successful reefer (and author) that does as close to 100% water changes as possible. He leaves just enough water in the bottom of the tank for the fish to splash in until he can add the new water to the tank. I just go with whatever is comfortable to mix, if I were using a 2 gallon bicket for example then thats about the size water change I would do.

 

[The Kapenta Kid]

Thanks, I just wanted to establish this. Indeed, using the nominal tank volume just gives you a safety factor or bonus.

 

[skipm]

Keeping track of your tanks parameters will help you decide if you are changing enough water or often enough. If you see rising nitrates then you need more frequent or larger water changes.