The general rule for fish in a thinner tank is to make sure the fish will not grow too long. Your fish should have at least a 1” space between them and the walls however 2 ½”+ is recommended. That means that if your tank is 6” deep you should have fish 3 ½” or smaller or if your tank is 8” deep your fish should be around 5 ½”. The good news is that most aquarium fish fall under this category. You can refer to these charts to help you choose.
6” tank depth http://www.walltanks.com/picture_library/medium_fish.pdf
8” tank depth http://www.walltanks.com/picture_library/large_fish.pdf
To put a tank in your wall you are going to need some experience with electrical and knowledge of how a stud wall is built.
Plan out your wall opening. Is your tank going to sit flush or hang-out on one side? You are going to need to leave a gap on the left and right side of the tank. If you have a hanging filter that gap will have to be large enough for it. You will also need a minimum space of 5” above the tank.
Next open you wall. Secure your stud work around the tank to support it and the wall above. Make a nice flat base with plywood and shims. If the tank is hanging out of your wall the base will have to hang-out too.
Now run your electrical wiring. Place an outlet in one or both top corners of your opening. Do not place it in the center because it might get in the way of the light. Use a GFCI outlet, it’s important.
Next clean up your drywall. Mud, sand, mud again, sand again and paint.
At this stage you can put the tank into your opening and box it in with some trim. Make your own from wood boards or use premade baseboard trim. If needed you can make the top piece of trim removable or hinged so you can get in to feed and clean the tank. The larger the opening the easier it is to get your hand in. Keep in mind that you will have to cover the opening with trim so if it’s too large the trim looks odd. A 6” gap is what we recommend.
That’s it. A more detailed set of instructions can be found here:http://www.walltanks.com/picture_library/instruct_jumbo.pdf