How many watts can a normal household circuit handle?

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Thanks for all the input.

As a rough estimate I figure most tanks in the 75-120 gallon range with MH lighting probably consume about the same amount of power as each other on average. So the question is, for people with this size of tank, but not running anything else on the circuit (dedicated circuit for the tank only and not letting the wife run the vaccum cleaner on that circuit) is it causing the breaker to trip?