Take the fish out, put it in a tempory tank. Go to the shops, buy a new one then come back and fit it. Answer 1 is not incorrect, but failed to mention that the tank in which the thermometer broke, and from which the fish were removed, should have the contaminated water discarded, and the tank and all accessories which were exposed to the thermometer contents, thoroughly cleaned and decontaminated BEFORE RETURNING the fish to that tank. j3h
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