Dwarf chain loach

So I am applying to work at a fish store, and they have dwarf chain loaches and I've never kept dwarf chain loaches YET. But I would still like to lead costumers in the right direction. So any care guides that you view as extremely accurate? And also, many care guides say they need 30-40 gallons minimum, but they only get 2-2.5 inches, why is this?

 

So I am applying to work at a fish store, and they have loaches and I've never kept loaches YET. But I would still like to lead costumers in the right direction. So any care guides that you view as extremely accurate? And also, many care guides say they need 30-40 gallons minimum, but they only get 2-2.5 inches, why is this?

I haven’t kept them but my guess is that it’s because they need to be kept in a school and the larger the school the better. Also they are very active.

 

I keep sidthimunkis and yes, they prefer a good size group and are quite active. I only have 7 currently in my 40 breeder but should be upgrading to a 75 soon and plan to double their amount. They do not do well with just one or two.
And yes, mine are snail hunting machines lol! But I hate hearing the suggestion to get a couple of them for that purpose.

 

Thank you, btw I meant dwarf chain, I didn't specify inside my post, only in title.

 

The reason they require a large tank is they are extremely active and love to swim. They are generally peaceful but should not be kept with extremely timid fishes that might be startled by their constant movement. As far as i can tell they are more than happy to swim to the top as stay at the bottom so you can never be certain what area of the tank they will occupy. Last but least as others mention they all but require a large group; I would think 7 would be the min but it never hurts to have 15 or 20. Finally they are an endangered fish and just about 100% of the ones found in shops are tank bred.