For 41qt adult tubs I would use 11/12 inch heat tape. For 28/32qt tubs I would use 6 inch heat tape. For hatchling tubs 16 qt and smaller I would use 4 inch heat tape.
I would snake the heat tape and only use a single piece.
I would get a herpstat intro + or herpstat 1.
If you need more than 1 outlet/probe the herpstat 2 and the herpstat 4 are great options.
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