I am thinking of siliconing two pieces of acrylic in between my 6x2 225 gallon glass tank as a brace since i received it broken. Is this safe and how thick and whats a good width it should be?
Silicone doesn't stick well to acrylic. At least for the purpose you will need it for. Acrylic is better glued with acrylic glue and glass is better siliconed. If I were you I would try to get glass because I'm not sure if glass to acrylic will go too well especially for bracing purposes.
Short answer is no...silicone does not adhere to acrylic, especially for a brace like u intend. Silicone is for glass and u should replace the top tank trim with a eurobrace using glass or the entire trim itself. A divider type brace will work using a piece of glass/silicone as u intend, not acrylic.
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