What is a 20x tank?

Hey, just curious here, I know what a 20 gallon long is, and I own a 20 gallon tall, so I obviously know what that is, but I keep seeing 20x gallon tank credentials on aquarium hood descriptions and what not. What is a 20x tank?

 

My guess would be a 20 gallon extra high.

 

I’ve never seen that, but that’d be my guess.

 

So would that be like a 20 gallon long, but turned on it's end so it stands up tall??

Edit: I just looked up 20 gallon extra tall instead of 20x (wow, good job me! Lol) it's pretty cool. I never knew such a thing existed.

 

It's not ideal for fish though, as the footprint is the most important (as fish use the horizontal rather than vertical space). Or plants, as less light goes to the bottom. My childhood tank had similar dimensions and didn't do very well at all.

Tanks like that are more common in the UK, where there is a trend for deeper aquariums. No idea why. I'm jealous of all you US people with your nice long shallow tanks.