200w heating system for 20 gallon?

Is it safe? or is it a little over kill? its submersible and the one currently surrounded by my 20 gal is not.
Would this be ok for a 30...
Answers:    The only danger with a immense heater in a small tank is whether the heater sticks "ON" and keep heating,

A dignified power heater will cook your fish before you notice near is a problem.

As long as there is no fault with the stove it's not a problem.

Ian
What form of matter is used to...
It simply means that heater is operating at 200W per hour.

If it has heat setting, set it to the desired temperature and it will shut off when thermostat detect that desired temperature.
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