Not bad at all.
What is your size of the tank?
Now I can see where the mess came from. :lol:
Some advise and pointers.
Reason why silicone did not stick to glass, you need to wash your glass. When glass comes from the factory or cut from the glass supplier it is covered with oil and dirt and not to mention paraffin when it gets cut and your paraffin you used to cut the glass. I wash all my glass and dry it off before I start sticking anything together.
I also pre-build all the tanks before I touch them with silicone, as silicone can be a bit oily and cause the tape not to stick.
When I say I pre-build my tanks, I use masking tape or silo tape.
I apply the silicone and then stick the tank together using the silotape/masking tape this makes the tank a solid cube, you could even use the tank as it stand. whistle2
Another method, or the method that gets used from the people who build fish tanks, they put a small layer of silicone between the glass and join it together first, this way your tank is strong and your tank is water tight.
The above method require 2 hands or some nice clamps.
Use a grinder or a belt sander to sand the sharp edges, it is faster and cheaper and saves your fingers from getting cut if you miss a couple of spots or don't do it properly or take it to the glass shop and ask them to erase it for you, should be about R5 a pain of glass.
They also use a belt sander, they have wet and dry sanders as well.
With building your tank you need to take time, you can't rush through the process of building tanks.
I normally cover the panels of glass with news paper, only leaving the edges where the silicone must join, something like you did.
This way, the silicone can mess on the news paper and not on the glass.
It also allows you to smear the silicone with out worrying about getting it on the glass.
It makes prep time longer, but when it is time for getting your tank ready it is so much more faster, you don't have to worry about cleaning (that much) your tanks out of silicone as the news paper has every thing on.
With pulling off the masking tape, you need to cut along the outline of the masking tape with a stanley knife of a blade, this will separate the tape and silicone and you wont have the tape tearing the silicone.
It is also better to wait a couple of hours days before you start pulling the masking tape off.
Pulling the masking tape while the stuff is wet is asking for more headaches than what the tank is worth, this also allows for a bigger mess with wet silicone on masking tape laying around on the floor, it also makes your hands full of the silicone.
I use a plastic putty scrapper that you buy from the part shop or paint shop, cost you R3, I then cut a corner off of the plastic scrapper.
I use this to apply and scrap the the excess silicone into a nice "triangle shape" it saves you on silicone and it looks neater, this is also where the masking tape/news paper comes in handy.
The cleaner you keep your hands, the less silicone you will have to clean up.
The more tanks you build the better you get.