What am I doing wrong?[(Xycraft tank)Solved]

[Guswut]

try replacing all the walls and corners with cobble, see if it works.

I really hope that doesn't work/means everything needs to be the same material.

 

[Dravarden]

it doesnt, is just to make sure he cleaned everything/not doing it wrong.

 

[ApSciLiara]

Yeah, he messed up the dimensions of the tank. He has an external wall that's 13 blocks long, and the max is 12.

 

[NosePicker5555]

Alright.. I had 1 piece of gravel on the side Thanks to everyone who helped