PlanetCatfish.com

I think corydoras and other bottom feeding catfish enjoy sand that isn't smooth. My corydoras seem happy in sand that is shaped like dunes. If they get scared they always hide behind the closest dune. What are your thoughts?

I don't think they are particularly bothered about flat or not flat sand, as long as there are some structures to use as shelter - dunes, plants, rocks, caves, etc.

I would have thought that eventually, the sand will flatten, given the activity of the corys, tho'.

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Mats

It makes sense that catfish would appreciate something to hide behind. On the other hand, sand waviness (or even sand presence) depends on what habitat you're in. Just because a cat likes a sand dune doesn't mean it wouldn't also appreciate a stick of similar shape and size to hide behind. In other words, catfish undoubtedly prefer a more complex habitat when it comes to hiding, but are probably happy just to hide behind anything, whether it's a sand dune or anything else.

From an aquarist standpoint, there is the maintenance issue of keeping sand with dunes. As Mats notes, sand will probably eventually flatten out. There is also the issue of the possibility of anaerobic pockets forming in the sand, building up toxic substances such as hydrogen sulfide (rotton egg smell).

EDIT: I just reread Mats's post and realized he basically said the same thing much more concisely, hahaha.

Well, it does eventually flatten, but it isn't that hard to rebuild.