Is it okay to build a 7feet long 1 feet wide aquarium?

It's possible to build a tank of practically any dimension. Just a matter of selecting the right glass and bracing to hold it all together.

With a long tank like that you probably want to go with internal glass bracing, which would be a strip of glass flat inside the tank along the 7 ft length, with extra pieces tying the front and back together. Maybe 2 front / back bracing stips? Now the front and back panes can't flex apart and crack.

The height of the tank is the main factor when working out the glass thickness. More height, more water pressure, and it's distributed over a taller area.

Also consider the stand, it's needs to be perfectly straight and level. No matter how well you build the tank, if it's not supported properly, it's going to fail.

But those are all just technical issues to consider, not things that make it impossible to build.

Ian

Yes that's fine depending on what type of fish you put in it. it wouldn't be okay with a fish that grew longer than 12 inches, but as long as you don't get giant fish that's no problem

Should be fine as long as it is braced correctly on the top and the glass is thick enough.