Part 1: Materials

Glascutter

Buy a good glasscutter, it will save you glass. The good ones can be bought at a glassstore, and you'll get some decent advice. They may also cut the glass for you when you buy it there. If you decide to let the store do that you can skip this part, and go to the calculation section.

Oil

Glasscutting requires a special kind of oil.

A metal lineal

Silicon Kit

This requires a special Siliconkit. It has to be specified on the kit that it's suitable for aquarium use, otherwise do not use it. The only ones I came accross are the transparent ones.

Measurer

Clamps(90 degrees, large enough)

Glass

Part 2 - Calculation

First decide on the measuremets of the tank. Some common measurements in stores are 100*50*50(L*W*H), 80*40*40, 60*30*30, but you may also want to create a labyrinth fishtank 100*50*35 which will be used her as an example. The glass thickness chosen for this thank according to the above shown table would then require 0,4 mm.

First the ground plate, which would then be L*B (example 100*50)

Then the 2 side plates B*(H-0,4) (example 50*34,6)

Then front and back (L-0,8)*(H-0,4) (example 99,2*34,6)

Part 3 - Glass cutting

Determine the thickness necessary for your tank, and buy the glass you need.

Mark the glass with the measurements(Use a CD-marker or similar). Oil the glas over the line you plan to cut. Place the metal linial on the glass. Best is to fix it to the glass with for example a glueclamp.

Place the glass cutter on the glass where you want to start the cut. Make sure you apply enough pressure. Now in one stroke cut the glass. Repeat if neccesary.

Place the glass on the side of a table, with the cut a little(0.5 mm)over the edge of the table. Place something heavy on the glass on the table. Ok. Now with a firm grip on the glas break it by bending it down with a snap, meaning you apply all the pressure downwards at once. The glass will then break along the line. Be carefull, it's now really sharp!You may want to use a diamond tipped file or similar to smoothen it a bit.

Part 4 - Assembly

If necessary clean the glass with ammonia to remove all fat(Dont use spiritus or alcohol, they are fat themselves). Place the bottom plate on a large enough worktable. Now go and change into those working clothes(Or do as I do, and get into trouble with your spouse)! Open the siliconkit, and put a 2-3 mm diameter wormlike line on the long part of the bottom plate. Do the same for one of the short sides. Put a bit of silicon on the long part and a bit on the edge where the first side plate will be placed. Silicon the bottom of the side plate a little bit. Where the side plate will be against the long front/back apply the same wormlike line.

Place the long front/back. Hold it at an angle of 90 degrees. Place the sideplate (bottom first) on the bottom plate. Slowly move it towards the front /back glass till it's also 90 degrees. Use clamps to hold it in place. The other two parts are done the same way, one after the other. Apply some extra siliconkit on all the connections from the inside. With a wet finger strike the silicon into a nice layer.

Let the whole setup dry for at least 12 hours. As long as you smell the kit it isn't dry enough. After this fill the tank with water let it stand for a day. Check for leaks.

Do a full change of the water three times during the next three days. The tank is now ready for use.