I Recently decided to get a heater to keep the water temperatures higher for my betta. This heater will overheat my tank if I am not watching so I only turn it on during the day.

One night I had left my window open and I woke up to my betta laying on the bottom because the temperature had dropped to 19 degrees Celsius. I quickly turned on the heater and the water temperatures have now been fine however he is still laying on the bottom. I do not see any physical signs of disease or sickness and he will not eat his pelleted food. I am worried that when the temperature dropped he was shocked by it.

He is currently in a 2 gallon tank.

  • Hi Noah! It sounds like you need to review your husbandry on your betta fish as this is likely the cause of his demeanor. I recommend checking out this answer pets.stackexchange.com/a/17545/7526 and make some changes to help your betta fish :) Sep 4, 2017 at 22:56
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    Get a heater which doesn't overheat the tank or allows the temperature to sink dramatically. Sep 5, 2017 at 13:19
  • a thermostate controlled heater is needed for all fish tanks even if one have cold water fish,a too variable temparature is bad for all fish and it might shorten the lifetime of the tank itself. Jan 10, 2018 at 10:30

1 Answer 1


Consistency is key. You are quite right that a large peak or trough in temperature can have adverse affects on the fish and is sometimes known as temperature shock.

You want to do everything you can to avoid large swings in temperature, PH, GH etc because the fish struggle to adapt to it (which also includes water changes - the new water should be as similar as possible to the old water).

To stop this happening again, get a heater for your tank which has an adjustable thermostat so that when the water temperatures reaches the correct level, it shuts off. You'll also want to place the heater near the outlet of your filter so that there is a reasonable rate of flow to ensure the water temperature is consistent across the tank and there are no 'hot spots'.

After a shock, some fish may not eat for a day or so - just make sure your water is pristine to help them and don't overfeed to compensate.

Generally, the more space you can give your fish, the better it will do in your care. I'd say, in my opinion, 2 gallons is too small to keep a fish and I'd definitely have it in at least 5 -7 gallons.

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