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emeraldking

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Like Essjay has already mentioned, and a lot of subtropical fish are suited to keep at room temperature (so, no heater needed).
 

Kyshiara

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The only problem with not having a heater is if the temperature fluctuates too much. For example, is it is room temperature and it is say, 18 degrees, then at night if the room temp drops, so will the tank water, which can cause stress to any fish.
 

emeraldking

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The only problem with not having a heater is if the temperature fluctuates too much. For example, is it is room temperature and it is say, 18 degrees, then at night if the room temp drops, so will the tank water, which can cause stress to any fish.
That depends on the kind of fish. For there are several fish species that have a wide tolerance in temperature. And in wild nature, those fluctuations are a reality and fish just survive without a problem. They can dive into the plants or go deeper. That's how it works. But again, it does depend on what kind of fish you'll choose.
 
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dubblejd

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A lot of fish sold as cold water fish in shops are actually temperate fish, which means they are OK at around 18 deg C. If the room the tank is in will be at or above that temperature in the middle of a winter night, that's fine. But if it gets colder than that, a heater would be advisable. It would need to be set so the water doesn't drop below 18, and the heater would only switch on if the temperature did drop in the middle of the night. A safety net. Since heaters are notoriously badly calibrated I would test it in a bucket of water so you can find the setting which turns on and off at 18 deg C.
Thanks for the advice. I actually put a thermometer in and am reading that it’s 12 degrees so I will be cautious before putting in fish. Can you recommend a low energy heater?. Thanks
 

Essjay

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Roughly speaking, a heater needs to be 1 watt per litre water. So a 100 litre tank needs a 100 watt heater. Going for a lower powered one, with tropical tanks at 25 deg C at least, means the heater will be on longer and can burn out faster.
A higher rated heater will heat the water faster and not be switched on as long. So yes, it'll use more power while on than a lower watt heater but will be on for less time.

With a heater set for 18 deg C, it won't be on much, it'll just sit there switched off waiting for the temperature to fall.


As for which brand, I use Eheim heaters. But whichever you get make sure it is variable. There are preset heaters out there which heat the water to 25 deg C and can't be altered.
 

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