Cory Catfish are one of the easiest and most popular catfish to keep in an aquarium. Corydoras are known to be hardy fish that are flexible in their temperature preferences, yet they’re often not treated well. So what’s the best temperature to keep Cory Catfish at?
How warm should Cory Catfish be kept?
The best temperature to keep Cory Catfish at is between 70°F (21°C) and 78°F (22°C). The ideal temperature depends on the species, some species like Corydoras sterbai like to live in higher temperatures (up to 86°F), while other species like Corydoras paleatus can do fine in lower temperatures (>59°F).
Cory Catfish species and their desired temperature
Did you know there are 156 recognized species of Cory Catfish? Even though I will not discuss them all, there are some differences per species to take into consideration. Especially if you plan to keep your Cory Catfish in a community setup with other fish, this will become handy to base your choice upon.
Bronze Cory Catfish (Corydoras aeneus)
Albino Cory Catfish (Corydoras aeneus)
Black Cory Catfish (Corydoras venezuelanus sp. black)
Sterba’s Cory Catfish (Corydoras sterbai)
Peppered Cory Catfish (Corydoras paleatus)
Panda Cory Catfish (Corydoras panda)
Pygmy Cory Catfish (Corydoras pygmeaus)
Tail Spot Pygmy Cory Catfish (Corydoras hastatus)
False Julii Cory Catfish (Corydoras trilineatus)
Julii Cory Catfish (Corydoras julii)
Salt and Pepper Cory Catfish (Corydoras habrosus)
Emerald Cory Catfish (Corydoras/Brochis splendens)
Gold/Orange Laser Cory Catfish (Cw010)
Green Laser Cory Catfish (Cw009)
Barbatus Cory Catfish (Scleromystax barbatus)
Adolfo’s Cory Catfish (Corydoras adolfoi)
Smudge Spot Cory Catfish (Corydoras similis)
Twosaddle Cory Catfish (Corydoras weitzmani)
Bandit Cory Catfish (Corydoras metae)
Delphax Cory Catfish (Corydoras delphax)
Skunk Cory Catfish (Corydoras granti)
Robust Cory Catfish (Corydoras robustus)
Horseman’s Cory Catfish (Corydoras eques)
Main Source: PlanetCatfish.com
Do Cory Catfish need a heater?
In most circumstances, Cory Catfish need a heater to thrive. They originate from the Amazon basin, in the tropical rainforest. Because of this, the optimal temperature for most species is above 70°F during the day. If you can reach this without a filter, this is fine, otherwise, a heater is needed.
The main reason I recommend a heater is because of maintaining a stable temperature in your tank and overall just feeling safe. Still, as Cory discusses in the above video, aquarium heaters tend to be overused.
Why? Your Cory Catfish are hardier than you think, and they can do fine for a long time in lower temperatures. Even in the wild, especially during nighttime, temperatures can drop significantly.
Whether you use a heater, in the end, is up to you – I personally use heaters to maintain a stable temperature and just feel more comfortable knowing I have an extra backup if needed.
If you want to save on energy, you can set your heater at the same temperature as your room temperature so that it will only turn on in emergency circumstances. This way the temperature in your tank will remain stable.
Another thing to take into account is the other stock. Even within the Corydoras genus, there are more sensitive species. Cory Catfish might do fine in these lower temperatures, but certainly not all fish do.
The last thing to consider is whether you should use a heater or not are your plants. Aquatic plants grow faster in higher temperatures, and some can even be sensitive to big fluctuations. In a well-planted setup maintaining a higher temperature are a good choice.
What happens in water that's too cold?
As we discussed above, most Cory Catfish species are rather hardy. They can withstand lower temperatures for long periods of time, and often do well at lower than often claimed temperaturs.
However, when the temperature gets too cold, Cory Catfish will become sick and die. Here are a few symptoms that show your water is too cold:
- Slow, inactive fish due to lower metabolism
- Lower immunity, causing the fish to fall sick more easily
- Lower reactivity to food/movements
This is why I recommend keeping Cory Catfish at a minimum of 70°F (achieved with or without a heater). At this temperature, most species do fine, especially because they are most likely used to that in the breeding facility/store.
Note: if you notice your tank is too cold, it’s extremely important to slowly and gradually higher the temperature of the water. Otherwise, your fish will die of temperature shock!
What happens in water that's too warm?
Oxygen dissolves better in lower temperatures, so one of the first things that will happen is an oxygen crash. This has two main devastating effects:
- Fish will not be able to breathe anymore.
- Beneficial bacteria will die, causing spikes in ammonia, nitrites, and nitrates.
Here are some signs your fish is suffering from a too high temperature:
- Rapid gill movement
- Faster swimming and being more reactive
- Gulping at the surface
What to do when water is too warm
First, try to find the cause of this problem. Make sure to check whether your heater isn’t broken and pull it out of the tank, since a broken heater might cause an overheated tank ( I’ve had to deal with boiled shrimp once, not very nice when returning from a trip).
But this can also be the case of just high temperatures outside or in your house, so then you’ll need to find a solution.
Here are some things you can do to cool down water:
- Use a fan to blow on the water
- Put a small amount of ice blocks in the tank (be very cautious, that the temperature gradually drops)
- Add colder water to the tank (again, be very cautious, so that the temperature gradually drops).
How to minimize temperature fluctuations
Temperature fluctuations are a big cause of stress for fish. Ultimately, this can cause a weak immune system and eventually lead to diseases. Especially if your tank is rather small, temperature fluctuations can occur.
Here are a few things you can do to minimize temperature fluctuations:
- Put your tank in a closed room or far from a door
- Don’t put your tank near technical equipment such as freezer or airconditioning
- Insulate your tank using wood or styrofoam
- Don’t place your tank in direct sunlight
Many Cory Catfish species prefer a temperature of between 70 and 80°F. There are species however like C. paleatus that do well in temperatures upwards of 70°F.
Overall, Cory Catfish are quite hardy fish. This makes some species able to live without a heater. Whether you use a heater is up to you, it is certainly beneficial to keep a constant temperature, many other fish prefer warmer water and plants grow faster in warmer temperatures.
If water is too cold your fish’s metabolism will drop, causing lower activity levels and lower immunity.
Water that’s too warm on the other hand causes an oxygen crash, causing fish to gasp at the surface and many beneficial bacteria to die. You can do a couple of things:
- Set up a fan to blow at the surface, and open the lid.
- Take out the heater and check whether it’s broken.
- Add colder water / ice (be very cautious to gradually drop the temperature of the water)