Hi, all you Cory-lovers...
my name is Heiko Bleher and I just have done several lectures in Europe on biotope aquariums and including those for Corydoras species. Most of these South American beauties live only over sand and soft substrate NEVER over rocks, pebbles or stones (except for maybe visiting them).
I feel really sorry for all of those fishes (cories) you really keep WRONG. Specially I want to mention briefly:
Kateyoup's sterbai are doing very well, one can see it, but
Joeshmoe; Girlofgod; Love–my-fish (this is terrible, and NOT love how you keep those cories); Jinithith2's peppered are totally unhappy because they do not find their food in the substrate; and I really feel bad about Simplysplend's panda, they feel lost (don't you see that?); same as Lupin's panda, which are already very skinny because they cannot get to the food and are damaging terribly their snout in these large rocks; at least sweetwaterarabians (whataname) has some sand and they look healthy and also Megk's look very good over the sand; but not Falina's and not Mirta's (very unhappy on those black rocks); same as Jeaninel's trilineatus, which also want to dig into the substrate and cannot...; beetleb2's trilineatus ae also lost and so does the new schawrtzi Jeaninel bought.
And I will ot mention the albinos shown.
Don't you all Corydoras-lovers know that those fishes have evolved through millions of years and adapted to the substrate they live on (fine sand or soft substrate)? Don't you all see that they are built for that? Their snout is evolved to dig into the substrate from where they always look for food (microorganisms, detritus, etc.). That is their niche, not rocks, pebbles or fancy stones...
I have collected Corydoras since I was a boy in Mato Grosso (with the age of 8 years old living with my mother and Indians discovering Corydoras sterbai, C. guapore, C. caudimaculatus, C. haraldschultzi, C. araguaiaensis, C. xingunesisi, etc.) and on more than 300 expeditions in the meanwhile in Amazonia and NEVER found a single Corydoras on such substrate.
I can only tell you all: it is a crime to keep fishes this way. It should be prohibited. You can compare it with yourself. Do you want to live 24 hours on a concrete / cemented floor and eat from it? Think about it.
All the best from one who loves fishes and wants that they love me as well,
PS: Why not give them a Christmas present: a soft sandy ground...