Total water volume

[Chutton47]

So really noob question here....I am starting a 40g with 29g sump.
When things refer to tank size are they talking about total volume or just the DT size?

 

[Animagus]

Usually just the DT size.

 

[shifty51008]

for equipment I add in the size of DT, sump and fuge.

 

[JMorris271]

When you are adding salt, meds or whatever, base your doses on total water volume of the tank and sump less volume lost due to rock.

 

[thomas.torode]

It depends.
Supplements, Volume.
Equipment, Volume.
Fish, DT.

Keep in mind Rock and Sand. JMorris271, is absolutely correct. ^^^

 

[BigEZ77]

For equipment, water changes, etc., its total water volume. For livestock, it should be display only.

 

[CStrickland]

I only think about total water volume for medecine really. Even with supplements you're just using it as a ballpark estimate to guess how much X you'll need to raise your level Y ppm, you're still going to test the actual numbers. But it's important to know if you ever have to treat the tank for something, and I reeeeally wish I had kept track of how much water it took to fill my system the first time. It would've been so easy and I'd know for sure.

For equipment it depends. Skimmer tank size ratings are trying to guess how much poop is in the water, so they'll say "heavy bioload 40 gallons" meaning something like 10 big-pooping fish, a crowded tank.

For fish, minimum tank sizes are about several factors: personal space, room to swim, opportunity to forage food, and more. A standard 120 is 4 feet long, a fish that needs that much tank might need the length for exercise, or the 120 gallons of space to not feel cramped.

So it matters what you're using the tank size for