Hi,
Whenever I try extruding in, I get a weird edge in the middle of the tank where the mirror is at
Looks like you've got a Face where it's mirroring:
with Mirror you can't see that:
until you extrude and scale:
It is what is called an inner face (inner, when the Mirror is taken into account) and should be (afaik always) be removed. Can cause a lot more problems than in this example;)
I did have a face, but deleting it didn't solve the problem
I can move the faces fine, but if I try extruding, then moving
I still get that extra face that doesn't move
Just delete those two extra Faces (or even easier the one Vertex on the corner)
Or enable Clipping in the Mirror Modifier to prevent this behavior in the first place;)
clipping didn't seem to fix it, but deleting the faces sure did. thanks for the help !