tryin to fix cracked glass on bottom

If you silicone 1/2" glass over the entire cracks and dry properly it should hold water no prob, but that doesnt go to say it wont be fragile, just be careful adding medium to lg decorations! I would use a whole tube of silicone press the new glass panel in and leave something very heavy to ensure bonding. They sell precut or specific cut glass sheets in various widths at LHS

you are better off replacing the bottom glass.

Lhs=local hardware store. They can precut any size u need man

any kind of fix is gonna cost you some money.

Get another glass piece the same size and thickness of current bottom panel or if you're brave you can try plywood waterproofed w one of the cheaper methods like drylok, but its risky to say the least.

Umm, if it's tempered glass it would shatter not crack. I doubt you have tempered glass.

All you need is a piece of glass big enough to go over the cracked end of the tank on the inside. I have a 135 that I fixed with a 12" piece of glass fit to the width of the inside of the tank. I'm about to fix a 300 with 3 pieces of glass over the existing cracked bottom.

Wash the inside of the tank, at least the area you're resealing with distilled white vinegar and water 50/50 then dry well with paper towels.

Put silicone over the crack, zig zag it on the piece of glass and right next to the edge, so some will ooze out when you press it down. Use a plastic spoon to smooth out a bead around it. (Don't use your finger unless you asked the glass place to ground the edges otherwise you'll slice your finger)