Cory cats acting strange

[Alice B]

Thank you. From what I've seen their natural substrate in the wild consists of sharp gravel. I did some research and found that they swim middle when they are in a new envorment. As I am typing this I am watching them and have not seen them swim unaturally all day since I got home. They were glass surfing and not in the middle of the tank.

I got away with corydoras on gravel for years, and I got some nice bronze cories and set them up on a mix of small and large gravel, and I lost a couple. I was told on here to go to sand. Had another cory acting funny after he ate a piece of small gravel. While I watched he ejected it thru his gill. I changed the tank. I was using undergravel filtration so I used a colander to separate out any gravel that would fit thru its smallest openings. I took out half the filter plate, put sand on the end away from the lift tube, no filter plate under it, and put the larger rounder gravel back in on the filter plate side. I'm using air driven U/g so I won't tear up a powerhead with sand. It's worked out very well. The slightly injured corydoras lived and no others exhibit any injury at all. I think I have all one gender, because no eggs, no babies, so maybe I will quarantine some more next summer. They love the play sand end of the tank, although they don't mind hideouts on the gravel side.

 

[Byron]

I noticed this when I had sand. Will BioStratum work? The pellets are something like 0.5 to 1mm.

Plant substrates like Fluval Stratum (I assume this is what you refer to) are not advisable for any substrate fish because primarily of the bacterial issues. I am not a microbiologist so I cannot explain the technical, I simply take the word of the microbiologists and others who do know. Large-grain substrate of any material has similar bacterial issues.

I also find it puzzling why so many continue to advocate for something which is clearly contrary to the genetic makeup of the species. If people treat a dog similarly, others would be setting the Human Society on them. It is fact that all cory substrates in the habitats that have been discovered and explored have sand or mud/silt, or a combination that always includes sand. The fish are genetically programmed to feed the way they do which requires a substrate they can filter and expel via the gills. What is so difficult to understand?

The species of Corydoradinae in Scleromystax aree considerably larger and presumably more robust. In describing two new species from different habitat ranges, this telling comments on the substrate: are instructive:

Scleromystax reisi was found mainly in very small (0.5-2 m wide) and shallow streams (30-60 cm depth), with slow current water and surrounded by relatively preserved riparian vegetation. The bottom was sandy, sometimes covered with a thin layer of mud or fallen leaves. Although there were rocky bottom stretches in the same creeks, the species was never found there. The streams may have a small amount of submerged vegetation.

Marcelo R. Britto, Clayton K. Fukakusa and Luiz R. Malabarba (2016), “New Species of Scleromystax Gunther 1864 (Siluriformes: Callichthyidae) - extending the meridional distribution of genera endemic to the Atlantic Forest,” Neotropical Ichthyology 14 (3)​

Habitat and ecological notes. The type locality is a small pond near the arroio Molha Coco. The pond is surrounded by grass and is partially shaded by low trees and bamboo shrubs. The water is clear and slow flowing, and the bottom is formed by rocks covered by a thin layer of mud. The pond is fed by a very small creek and is periodically flooded by the main stream. Other species collected along with Scleromystax salmacis at the type-locality are Steindachnerina biornata, Mimagoniates rheocharis, Astyanax scabripinnis, Hollandichthys sp., Rineloricaria aequalicuspis, Pareiorhaphis nudula, and Phalloceros caudimaculatus. The rio Ratones, on the other hand, has a sandy bottom and specimens were collected on an open, sand bank.

Marcelo R. Britto and Roberto E. Reis (2005), A new Scleromystax species (Siluriformes: Callichthyidae) from coastal rivers of Southern Brazil,” Neotropical Ichthyology 3 (4).​

 

[anachrotech]

I am correct here because I have spent considerable time doing research from those who know, the collectors, ichthyologists, biologists who have worked with every so-far discovered species of cory.

I had a feeling that misleading video on AquariumCo-op would likely be behind this. Ian Fuller, who is the recognized authority on Corydoridae put the lie to the video. It is misleading because it shows a handful of "gravel" which the text says is the substrate. But that is false. I told you earlier that some species liv over a mixed substrate, and the one in this video is such a cory. And if you take a handful of substrate from another area it would be sand. There is actually a fair amount of sand in the video site, but of course they do not tell you this because it does not suit their purpose. If any cory were actually found over sharp substrate, I can assure you their barbels would show it. I had this occur some years ago when I foolishly set up a tank with Flourite; within one week all the 12 cories has stunted barbels, and one panda even had about a quarter of its lower jaw sliced off. They all recovered when moved to a sand substrate tank, and lived for years.

Ian Fuller has been collecting cories and spawning dozens of species for 60 years. Heiko Bleher has been exploring and collecting fish from probably ever accessible habitat in Amazonia and beyond. They will both tell you without any reservation that you mut have soft sand. Cories filter feed; they take up a mouthful of sand (or mud/mulm), extract any food bits they might find, and expel the sand through their gills. This is how they feed, it is a prerequisite programmed into the genetic code of each cory species. To deny them this inherent need is inhumane.

As for internet sites, many are false and unreliable. Any idiot can set up a site these days. That does not mean they have the slightest idea of fish requirements. This forum aims to correct the misinformation, and there are reliable sites...for cories there is pre-eminently Corydoras World (Ian Fuller's site) and it has a FB page, there is Planet Catfish, and there is Seriously Fish.

My tank has had fluorite substrate and cories for a few years. None of my 20+ cories has damaged barbells.

 

[GaryE]

The aquarium co-op article linked is slack work. Their CEO went to "their( Corydoras) habitat"?

Which one among millions? Which species?

The solution is easy. Go to Youtube. Search Corydoras in the wild. Go to Ivan Mikolji's channel, and to Oliver Lucanus's below water channel. The video is there. You can look for yourself. Pay attention to whether the fish are feeding, or in transit over the substrate and migrating.

I have kept Corydoras with no problems on what I would call rounded gravel. You might call it sand. In gravel with sharp edges their behaviour is different. There is a lot less digging, which is their natural feeding strategy. You may get away with rougher gravel, but why? It's their behaviour that is so much fun to watch, and you'll cheat yourself while cheating them. They probably won't die, and barbel erosion may not happen. It has never happened here, in 56 years with Corys, and I only figured out using sand or sandy gravel about a third along this journey. The only barbel erosion I've ever seen has been shipping damage from ammonia. I imagine with overfeeding and large grained gravel catching the decaying food, you could create those conditions. You wouldn't much of an aquarist to let things slide like that, but.