Unfortunately I did this many years ago so have no pictures of the steps involved but I think the pictures I have will give you the idea.
WARNING: TV sets hold high voltage even if unplugged for a very long time.
1. Find a flat screen TV that suits this mod.
Any TV with a curved bezel around the front isn't suitable for this as the glass won't fit flush and ultimately you lose space as the tank would have to be thinner. ( mine is 65mm wide by 16mm deep so it fits flush up to a wall and you can't see the rear)
2. Pulling down the TV you need to be careful, as said tv's hold high voltage. Pulling the off the back of the screen/bulb is the problem. I used a towel and side cutters to cut the cable and I still got a shock!
I'm sure there's tuts online about how to remove them properly.
3. You will need to grind away some plastic tabs and screw mountings to make way for the tank.
Also cut away a section of the top for access. (Water filling/feeding the fish.
4.I have a friend that's a glazier so I was able to grind away and soft fit the tank to get a good fit which had me back and forth a few times to get it how I wanted it. Also I got the glass cheap! Cost me $50 to get the tank made and siliconed in.
As you can see by one of the pictures I put foam under the tank to support it as once it's filled it weighs quite a bit.
Unfortunately being the first time I had done this I didn't think about emptying and cleaning and had I done so I would have fitted a drain tap at the bottom!
Something to think about as once full again weighs a lot and it have to use a cup to empty it 3/4 of the way before I'm comfortable tipping it over to empty fully.
This is a very cool mod and I've had orders from many people to build them one. Kids also love it!
If you have any questions please don't hesitate to ask.