Why don't corys like black sand?

[anewbie]

This has come out of the blue (lol) but might as well be answered. Both species C. aeneus and C.eques are in lineage 7 so technically they could hybridize. However, if a sufficient-sized group of each is in the aquarium, so that both genders of each are present, this is highly unlikely. It is when there are not both genders of each species that cross-spawning is more likely to occur.

Btw my equeus love black sand; as to why this came up - i have orange laser (c. aeneus) in one aquarium and a group of eques in another aquarium and i was reviewing where i was going to move fishes after i move.

 

[denogginizer]

Hello! I have a cory in my fish tank and would like to know why it does not like that type of sand. And if I were to change the sand, how would I change the sand without disrupting the black sand! Thanks!

This is just a personal observation, and not scientific... I have maybe 50 Corys in multiple tanks, all on black sand and they seem completely fine and healthy.

 

[GaryE]

I am going to darken the sand for my Scleromystax barbatus as I moved them into a light sand tank, and they are a dark bodied fish. I hadn't considered the issue of fear of birds. It's a dominant idea when I design killie tanks, but I simply overlooked that important lesson for these almost Corys. Tomorrow, when the lights come up, the substrate will darken.

edit: I just checked the photos I had when they bred, and I had a fine dark grey substrate. let's see what a mottled look will do with the light, fine sand that's already in the tank. Their patterning on the gravel too - I can do that!

 

[GaryE]

Okay, so I added some dark grey sand to a tank of S barbatus, a mottled dark grey fish. They have been in hiding since I moved them to a tank in which I hope to breed them.
I've barely seen them in 3 weeks.
If I had a beige Corydoras in that set up, I would have used beige sand. I want to see how they respond to gravel that matches their camouflage, and S barbatus are of a distinct base colour compared to my Corys.
So far, so good. They are out of hiding and all over their tank They are cruising through the caves, and not stopping in them. It's only been a few hours since I added the substrate, but the storyline in that tank is transformed.

 

[Byron]

Scleromystax barbatus live over sand in their habitat, and avoid gravel and rock areas even though these are found within the species' range. This abstract from a recent study on this species is instructive.

Habitat used by fish is often related with the requirements of the species, according to their morphological characteristics, feeding, and reproductive strategies. We describe the habitat preference, foraging behavior, and camouflage strategy of Scleromystax barbatus (Callichthyidae: Corydoradinae), an endemic catfish from coastal streams in the Atlantic Forest. The movement and foraging behavior of 11 individuals were observed using focal-fish method, and the habitat structure availability (i.e., depth, bottom type, and mesohabi-tat) was measured in a clearwater stream stretch with 40 m length and 2.8 m width (± 1.5 sd) in southeastern Brazil. In addition, six individuals were captured to verify stomach contents. Habitat selectivity of the species was assessed using the Ivlev electivity index that considers the frequency of occurrence of each habitat variable used by fish in relation to its environmental availability. Scleromystax barbatus selected pools and runs with sandy bottom in depths between 21 cm and 40 cm, and avoided gravel in shallower riffles (up to 10 cm). Individuals foraged close to the bottom in a head-down posture, speculating and revolving the substrate composed by sand, fallen leaves, and twigs. Their long snout and small barbels were used to dislodge the food items of the substrate, which were quickly sucked by the mouth. Aquatic immature insects (mainly trichopterans) were predominant in the stomach contents. Three fish species, Deuterodon iguape Eigenmann, 1907, Mima-goniates microlepis Steindachner, 1877, and Geophagus brasiliensis (Quoy & Gaimard, 1824), were firstly registered following S. barbatus during its foraging activity. The brilliant golden body color with darkish spots of S. barbatus strongly resembles the stream bottom, which indicates disruptive camouflage. © 2013 by Unisinos.(...)​

Gonçalves, Cristina da Silva; Cestari, César. "Uso de riacho costeiro da mata atlântica pelo limpa-fundo scleromystax barbatus (Quoy & Gaimard, 1824)," Neotropical Biology and Conservation, v. 8, n. 3, p. 115-120, 2013.​

The paper is not available free (and it may be in Portuguese) but the abstract in English and Portuguese is online:

Uso de riacho costeiro da mata atlântica pelo limpa-fundo scleromystax barbatus (Quoy & Gaimard, 1824)

repositorio.unesp.br