Use a piece of glass that is almost the size of the bottom. If you use a small strip the downwards pressure will make the cracks spread and youre back where you started.
A litre of water weighs 1 kilo. Work out how many litres it holds and thats your KG weight. add the tank itself, the hood, rocks and bogwood, stand et al, and you are up to a very serious weight. Make sure the floor will hold that weight without bowing or bouncing as someone walks by.
Use a good bead of silicone, like you would spread wood glue from a bottle before you spread it.
Just rest the glass on the broken bit and use some soft weights (piles of books or similar) to lightly compress the silicone.
Leave it TWENTY FOUR HOURS, OR YOULL BE BACK WHERE YOU STARTED AGAIN.
If the glass bottom is resting on any solid material, thats what cracked it. You need some 1/4" polystyrene from the pet shop to lay underneath it, or one minute piece of grit will crack it again.
A tip on the poly, you will find its a sheet the same size or bigger than your tank. That tank looks pretty heavy, so I would use 6" wide strips of poly across the base, with a few inches gap between each sheet. If there is a seriously heavy weight on poly the ends sag but the middle cant, so it bows, and youre back where you started again.
Once sealed and filled, DO NOT pile up a rock wall unless you silicone them together.
Many fish burrow in the gravel and I have seen a 6 ft tank destroyed by rocks falling down onto the base (not to mention several hundred pounds worth of fish dead because it happened while the owner was at work).
The fish that died was an opaline gourami. its a top feeder, so the way to stop them jumping is to lay floating plants across the top of the water. Then they can see the surface and will feed off the plants.
Feeding. Oh boy, to a fish keeper, thats a sharpening thread and a half.
Heres the FACTS.
Fish will keep eating, even when they are full. They have a valve that closes the stomach when full and allows the food to just go straight through. This allows them to always be full if a drought suddenly arrives.
Have you ever seen long strings of "pooh" from a fishes bottom? Theres too much food available to the fish.
Have you ever seen the fish in a dealers tank go absolutely berserk when you get near the tank? Theres not enough food.
The unscrupulous dealer will keep the fish starved
A/ to save money on food
B/ to save having to clean the filters so often
C/ to make the customer go "ooh look, they like me!" and buy something.
So, to recap, you can feed the fish as often as you like, but the QUANTITY is everything. If its still floating after five minutes youve put too much in. if they act like a shoal of piranhas when you go near, put more in.
Its a great hobby. I was given a 6 ft x 18" square tank made of 1 1/2"" angle iron with 1/2" shop plate glass. That was my first tank!
I ended up with a shop with 150 tanks selling ONLY fish.
Rather than bogging down the site, I'm always happy to discuss any thing else through the pm system.