Corydoras Eversi

By Don Kinyon

There is a soft drink that is popular in Brazil that is made from and named after the Guarana plant, which gives the drink an attractive yellow/orange color. It’s only fitting that a Corydoras catfish found only in an isolated spot in the same region and sharing the same attractive color should have the nicknames “Guarana”, and “Soda Pop Cory”.

Corydoras eversi is named for the editor of Amazonas magazine and long time Corydoras enthusiast, Hans-Georg Evers. It’s said that Evers was the one that originally collected the fish and brought it to Europe from an isolated, undisclosed location. Originally it went by its nicknames or the C65 designation, but in 2016 Tencatt and Britto did the description and honored Evers with the official name.

This is a very attractive catfish. They are mid-sized as far as Corydoras go, with the males reaching an inch and a half, with the females achieving slightly more. They have a rounded head and snout, much like C. sterbai or C. aeneus. Their color pattern is similar to many, with a light background covered with darker dots on the head, forming haphazard horizontal lines down the body and dorsal fin and faint vertical lines on the tail. The belly is white but the big feature of the fish is the yellow/orange base color; it’s very distinctive. I found this color can be brighter or more pale depending on the fish’s diet, lighting, and surroundings.

I was fortunate enough to do some trading with one of the most knowledgeable and experienced Corydoras folks around, Eric Bodrock. I got to pick out my own and ended up with four males and four females, if my guesses were correct. I brought the fish home and settled them into a 40 gallon cube-style tank with about 80% rain water and 20% well water. They made themselves at home and seemed to adapt quickly to their new surroundings.

Filtration was accomplished by two large bubble-up sponges and no supplemental heating was used. The floor of the tank was covered with about an eighth of an inch of fine sand and the only other pieces included were two floating and two bottom yarn mops (I found some camo yarn on special at a craft store and they make really cool mops!) The pH was at around 6.2 and the dissolved solids at around 70 ppm. Just a FYI: my pH tester is the old-school eye-dropper type so any readings are going to be approximate. The tank was unheated and the temperature varied between 70° and 76°F.

Feedings were twice daily: flake or other dry prepared food in the morning and live, frozen, or freeze-dried food in the evening. One of the first things I noticed was that this species didn’t eat as much as many of the Corydoras that I’d kept in the past. They didn’t even go after some of the favorite foods other species devoured with much gusto. This caused a minor problem for me, as I overfeed most every tank and the small appetites of these fish left food to spoil and foul the water. A few self-taught lessons in self-control were necessary to keep the water clean. The fish just don’t seem to need as much food as many Corydoras.

Another thing that is strikingly obvious once you get used to these beautiful fish is how slowly they grow. They grow painfully slowly. If you’re used to the growth rate of the C. aeneus  or C. elegans complex, you will wonder what the heck is wrong with C. eversi!

Once used to the smaller feedings, I found the fish very easy to care for. They got a 40 to 50 percent water change once a week, mostly to make sure they had enough clean water to keep them healthy and growing. Like most Corydoras, they were more active after the lights went out for the night. “Flashlighting” an hour or so after lights-out showed them digging around in the sand for the last of the food.

Once I’d had the fish a few months I noticed a few eggs on the glass while doing a weekly water change. It was behind one of the floating mops, right in the bubble stream of one filter. This was a surprise to me as I didn’t think the fish were mature enough to spawn. I removed the eggs to a hatching container and searched for more. In all, there were 10 eggs on the glass and in the floating mops: none in the bottom mops. The hatching container was a plastic shoe box with water from the breeding tank, a bit of java moss, and a small air stone. An alder cone was added to help keep any fungus from spreading.

After a few days, it was clear that the eggs were not going to hatch. They’d turned white and some had grown hair. Disappointing as it was, it also gave incentive to keep trying. Every day the tank sides and mops were checked for any sign of eggs and almost every day there were a few eggs on the wall again behind the floating mop. Again, I set them up into hatching containers and again they all went bad. This went on for a couple weeks and no eggs had hatched.

There isn’t much information on these fish on or off the internet, at least not that I could find with many searches, but Eric had given me hints on caring for the fish when I picked them up. With a nearly 100% water change using rain water, the pH dropped to 6.0 and TDS to 35. This wasn’t as acidic as he’d suggested, so I added an acidifier to drop the pH further to 5.5. This, however raised the TDS.

The fish spawned again, which they seem to do almost continually, and out of 14 collected eggs, one hatched; not a very good average so far! The next few spawns averaged about the same. Just to try a different approach, I did another large water change with rain water and left out the acidifier in order to keep the TDS down. Once done, the pH read 5.8 and TDS 23. It may have been my imagination, the group seemed more active than before.

Because sometimes work and life get in the way, it was over a week before I had a chance to check for eggs again. There was evidence that there had been a spawn, but the eggs were gone. It was another disappointment, but only for a few seconds. The floating mops contained nothing, but when I pulled up the first bottom mop, about a dozen tiny fry scattered! The same thing happened with the other bottom mop. Now there was a decision to make: leave them with the parents and take the chance them being eaten, or try to move 20 or 30 tiny fry to another container. They’d been there at least a few days and hadn’t been devoured, so I decided on the former: leave them. So, I got busy making more yarn mops and lined the entire bottom of the tank with them: let the fish take care of things on their own.

The adults and young fish did well in the common tank. Decapsulated brine shrimp eggs and Golden Pearls powdered food supplemented the feedings so that all would be fed. I found that the young fish have no better appetites than those of the adults and are easily overfed. This made it necessary to clean out the mops almost daily. Every time the mops were pulled from the bottom to be cleaned, more and more fry would rush away from underneath. Eventually, it became clear that there were going to be far too many fish in the tank, even though I’d been selling off a few every once in a while.  As the oldest of the youngsters were a little over an inch long at almost four months of age, somebody had to move out.

There was a group of tetras growing out in the tank next to my C. eversi and the water was nearly the same, so it was no great task to get it ready. By removing the heater and allowing the water a while to cool, I had a great place to house the adults and give the young fish more room to grow. Some of the oldest young went with the adults to add to the breeding group. The tetra tank had been clogged with java moss and was left that way for the Corydoras. As many of the tetras that I could catch were removed, but quite a few eluded capture and stayed with the catfish. It was two days later that I noticed eggs on the front glass of the new tank.

To make my life a little easier, I thought I’d use tap water in the grow-out tank.  With so many fish in the tank, water changes had to be frequent and I only have so much storage for rain water. Slowly, over a couple weeks’ water changes, the water was replaced with my tap water, which is around 7.4 pH and 140 ppm TDS. This didn’t set well with the catfish. They were less active, ate even less than usual, and just didn’t act right. Once they got back to about 75% rain water, all was back to normal.  

At one point, I found a can of Tabimin tablets in the freezer that had been hidden behind some other fish foods. Just to see, I dropped a couple tabs into the grow-out tank. The fish liked them! The adult fish went for them as well, so Tabimin became a steady part of the fish’s diets. I’m not trying to push any product, but these guys didn’t go for any prepared foods and very few live foods with as much gusto as they did with the Tetra tablets. It may work out different for others, but as for me, I ordered a big bottle just for the C. eversi.

At this writing, the oldest of the young Corydoras eversi are nearly five months old, and not quite an inch and a quarter. They’re active, healthy, eating little and growing so, so, slowly. The good news is, during a water change in the new breeding tank, I noticed a bunch of fry hiding under all the java moss. In a half year, they should be ready.

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Just as an aside, an odd thing happened in the second breeding tank set up. A few days after the adults and a few of the young were moved into the new tank, I was “flashlighting the tank after the lights were out and couldn’t believe what I saw. There were white spots with small filaments on all the Corydoras. There were still a few tetras and some pencil fish in the tank and they all looked fine: no spots. I could not believe it! It looked like Ich. I don’t get Ich! I was offended. The catfish acted fine even though they looked awful which made me feel a bit better. I dumped a cup or so of rock salt into the tank which brought the TDS up to 600 and in a couple days they all looked good again.