If you ask us to name ten freshwater fish that are mostly preferred by many fish keepers, Corydoras must be one of them.
Corydoras is a small South American catfish, belonging to the genus of Corydoras and family of Callichthyidae. They are generally found in small streams, along the margins of larger rivers, or marshes, ponds, especially those covered with dense growth of plants. People identify Corydoras by their two rows of overlapping armor plates running through the length of their body, sharp spines in their fins, and barbels on each side of their mouth. Their body, subject to specific types, may vary from 1 to 3 inches long. Such an ideal size makes them a perfect choice for small to medium aquariums.
Fun fact: Corydoras is named based on their appearances, a skin like a helmet. The name is derived from the Greek kory (helmet) and doras (skin).
For a long time until now, Corydoras has always been a suggestion for the beginner due to its hardiness, peaceful temperament, tons of interesting personalities, and easy-to-keep regardless of type.
Like other easy-to-keep fish, Corydoras are not picky about their diet nor living conditions. They can live in a wide variety of water types but tend toward soft, neutral to slightly acidic or slightly alkaline pH and 5-10 degrees of hardness. Being tropical fish, most of their types will prefer the temperatures between 72 and 82°F. Corydoras are relatively sensitive to water parameters so maintaining appropriate ones and keeping them stable are very important. We suggest the following for your reference as these are generally suitable for most types of Corys.
Ammonia and Nitrite: 0 ppm
Nitrate: less than 20 ppm
pH: ranging from 6.5 to 7.8
Water change: 10% every week or 25% every 2 weeks
Note: Don’t let your Corys live in a high nitrate level environment as this ion will harm their barbels, which then shorten and become useless. Regularly check the nitrate level in your aquarium and perform the water change if it reaches the extent.
Speaking of living conditions, setting up an appropriate tank is an important step that we cannot skip. Although Corydoras are easy to please, a well-arranged home is still necessary. It not only enhances the quality of life but also prolongs the life span of your fish (with proper care and a little bit of luck, your Cory may live up to 15 years).
To do that, the first thing is to choose the right tank size. Corydoras has small size and prefers living in a group (in general, a group of six or more if you like). Hence, your aquarium may not be too large but should not be too small. A 10-gallon aquarium can be acceptable to those types having small bodies. In case you keep them with other fishes or your Corys are in medium size, you should consider the larger aquarium, a 20-gallon to 30-gallon is highly preferred. It is also important to cover your aquarium with a lid as Corydoras sometimes dart up to the surface to get a gulp of air.
Fact: They are capable of breathing both water and air and often enjoy this activity. However, if this happens in excess, this means your aquarium water lacks oxygen. Your catfish can live in a low oxygen water but this state should not prolong. Once noticing the alert, you should adjust the water conditions to promptly provide them with abundance of oxygen.
Upon your tank is decided, we then choose aquatic decorative materials. Corydoras don’t have any specific requirements about decoration. However, we recommend that you resemble their natural habitat. This will make your fish feel comfortable and familiar as well as encourage them to be more active and live happily. For your ease, let's discover a desirable well-decorated aquarium for Corydoras from the bottom to the top.
- Substrate: Smooth sand is preferable to gravel by most aquarists. Some gravels have sharp edges which will erode or affect Cory's barbels if frequent contact with. However, in the wild, Corydoras can be found on sharp substrate so they won’t have much problem whether you use sand or gravel. Despite the fact, we recommend that you choose round gravel or gravel without sharp edges if you still insist on this type of substrate.
- Live Aquarium Plant: Corys are timid. To help them feel secure or relieve stress when threatened, your aquarium should be covered with dense aquatic plants. This not only imitates their familiar natural habitat but provides shelters for them to hide as well. Some aquatic plants are highly recommended including Aponogeton, Java Moss, Java Fern, Crypts, Pennywort, Hornwort, and Peacock Moss. However, there is one more rule that you should notice. Corys are also active. Thus, when you arrange the plants, try to create some free space in the front of your aquarium to allow and encourage them to socialize.
Tips: If you use sand substrate, you may need root tabs to assist your aquatic plants in the first few months, as it can help such substrate absorb enough nutrients for the plant to grow.
- Lighting: Standard community tank lighting will be acceptable. However, since Corydoras originally live in slow-moving water which is shallow and very murky, they may favor dim light.
- Other decorations: Rock (without sharp edges) and driftwood can be added to provide them more places to explore. If you want to create an impressive aquarium landscape, you can put some colorful items there. Such items will give highlights to your aquarium as most Corys do not possess a bright appearance. Just note that no sharp edged decorations should be allowed in your aquarium.
Corydoras are also known as bottom dwellers or crew fish. This is because they like spending most of their time crawling on the bottom of the tank, using their barbel in search of food. They are not fussy about food and will eat anything small and soft enough to fit in their mouths. Therefore, live blackworms, frozen bloodworms, sinking wafers, or other sinking community foods can be acceptable to them (try to use high-quality ones). As crew fish, Corydoras could eat the leftovers, but this is insufficient. You must feed them once a day to ensure they take in enough nutrients to grow. Follow the old rule that only gives as much food as they can eat in 2-3 minutes.
Note: Though Corydoras are regarded as a clean-up crew, they cannot thoroughly clean your fish tank considering their size. So performing periodical maintenance is crucial.
Corydoras can be good tank mates with most community tank fish as long as they are non-aggressive and friendly in nature. Otocinclus catfish, tetras, swordtails and other Corys can be a good fit. If you want to keep them together with shrimp, you could consider bamboo shrimp, vampire shrimp, amano shrimp, red cherry shrimp or ghost shrimp. Some freshwater snails can also be the potential candidates, such as gold inca snails, mystery snails, ramshorn snails, pond snails, malaysian trumpet snails, rabbit snails, japanese trapdoor snails or nerite snails
When enjoying your aquarium landscape, you should occasionally observe your Corydoras to identify their health conditions. If you distinguish small white spots on their skin and fins, they may likely be affected with ICH. If it is the case, try to find the cause by checking whether there is any sign of poor-quality water or sudden changes in parameters, or you have done anything causing disorder to their living environment (such as excessively stirring up the tank bottom while cleaning (may lead to bacterial bloom), rearranging decorations). Immediately consult with a specialist and treat them with the right medicine. Also, clean your tank and/or keep parameters stable if that is the reason for your fish’s sickness.
Corydoras catfish are funny, we’ve told you they have tons of personalities. Indeed, in addition to what we have mentioned above, you may find
- they are very active a moment ago and then peacefully resting motionless in the same spot just in a blink.
- they are peaceful but not totally defenseless like other similar species. Because hiding in their sharp spines is mild venom which will be readily produced when they feel stressed or threatened.
And more which we believe you can explore by yourself when keeping them.