Best cleaner for glass before reseal

I've always had good success with 90% isopropyl alcohol (rubbing alcohol)

I know some people use acetone also.

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acetone

I know from experience that alcohol is pretty safe. I've resealed a few tanks using that to clean. It's less harsh than acetone

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The only thing I found to remove that film left behind from the old silicone is a wire brush. I got one to chuck up in my drill and a little wooden handle one for the tight spots. Don't worry it won't scratch the glass (or maybe I just got lucky). Having recently completely disassembling a 125 gallon I bought, I spent a few hours trying several different methods off YouTube. In the end it came down to some good old fashioned elbow grease.

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