I just looked up heater requirements for a 50-60 gallon tank and it looks like you are pushing the upper end for your heater as your 240 liter tank equates to 63.4 gallons.
Recommendations for a 50-60 and it shows 200W.
Recommendations for a 75-100 gallon tank is 250W-300W.
So your 200W would do the job but would work hard likely shortening its longevity. Going with the ratio shown in the following link you should have a 221.9W heater which, of course, you won't find. I would personally consider a second heater but getting an additional 100W unit would probably do just fine and cost less.
Maintaining proper temperature in an aquarium is very important for the well-being of your fish. An aquarium heater ensures that the water temperature is
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