Hmm, good question. I have no clue. I would either offer it for free on Canreef or Kijiji, or call around to glass shops to see if they will take it. Presumably they do something with their glass scraps ?
I tried googling and people suggested to smash the glass and put it in a bag and throw it in the blue bin. I really don't like splinters
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You wouldn't want to see my tank. I don't use fancy equipment and I am a noob