Can I keep Cory with small gravel?

[MrsHyde1018]

Actually, the wrong question was asked in the thread title...the issue really is not if one "can" keep them on gravel, but should one. Putting the best interests of the fish first.

It is also impossible from the photo to know the actual grain size, as we don't have a scale. But if the grain size is larger than river sand to the extent that the fish cannot filter feed, then it is completely inappropriate. And all species of Corydoras are filter feeders because this is programmed into their DNA. Sand is frequently found in the gut of Corydoras fish, according to Ian Fuller; "Also complete bodies of ants termites and a host of other similar creatures. I am pretty sure the sand aids the breakdown of these animals."

Some members here respect Ian Fuller as one of the foremost Corydoradinae authorities. A new described species was recently named in his honour, Corydoras fullerii Tencatt, Santos, Evers & Britto 2021. Following are direct citations from Ian [no idea how to copy over videos, sorry].

May 28 "OK folks. With all the discussion about substrate. This is a video clip of a C. ornatus feeding on tubifex in the sand substrate. If the substrate particle are too large to be able to be taken up by mouth and ejected out through the rear of the gill cover then it is not suitable.
To avoid posts from inadvertently encouraging the use of inappropriate substrate, post with images showing anything other than fine smooth grained sand will not be accepted.
The same will apply to any posts defending the use inappropriate substrates. in both this and its sister group Corydorasworld Members Group page.
Ian"
Later in the same thread:
"It seems my advice was not headed and my delete button is found to be working very well."

May 31 "This will not be everyones cup of tea, but it bothers me not one iota. As of now pictures of Corydoras over inappropriate substrate will be rejected.
Our message to people wanting to keep and even breed Corydoradinae Catfishes is to do the right thing and provide what is the right substrate for their Corys, "Natural Sand"

Your reply brought a question to mind and out of genuine curiosity I’ll ask: if cory’s intake the sand and sort in their mouths, what about granule lava soil. (I say granule because the granules crumble when pressed.) they’re very smooth and not heavy.

 

[Byron]

Your reply brought a question to mind and out of genuine curiosity I’ll ask: if cory’s intake the sand and sort in their mouths, what about granule lava soil. (I say granule because the granules crumble when pressed.) they’re very smooth and not heavy.

I've seen your other thread on this, and posted. I doubt they are able to filter feed the lava soil, but it is obviously sharp enough to have destroyed their barbels (as you reported) and even parts of their mouths are apparently missing, and the bacterial factor is there too.

 

[itiwhetu]

As I said above. Nitrates are a bigger problem with corys loosing barbs than the substrate they are on. I have kept and bred many cory species and always on fine river gravel. Sand I believe is far to fine. I also don't class corys as filter feeders. The fact that they take sand through there gills maybe no more than they can't distinguish between that and the fine food that they are foraging for.

 

[itiwhetu]

It is interesting when you do a google search for Corydoras under images only about half of the images show the fish on sand.

 

[DoubleDutch]

Is there a grainsize at which we call something sand or gravel ? My Corys love sand and when I have the choice I'd always offer them PFS (mediumsized) but I have kept Corys at smaller grained "gravel" like this for years.
Most worn of barbells and issues occure in the larger pebble like gravel in my opinion in which food will get out of reach and bacterial / ammonia / nitrites will occure.
Sand can also be to dense (thata why I use mide eized PFS) and cause anaerobic pockets with the issues alike btw.

Funny thing is I visited Aqualife Leyland in 2016. All displaytanks contain gravel, what I thought to be rather strange as they ate well known for Corys and catfish.

 

[Fishfinder1973]

I have an 8 inch strip of sand along the front of my tank and the rest is small round gravel.
I can say this by experience,corydoras prefer to eat over sand 100%,and I watch the sand coming out their gills.
In saying that,if I only had gravel then they would have no choice but to eat over that.
The proof of the pudding is that they prefer sand,given the choice.

 

[Avel1896]

Hey
Texture must be smooth and polished to save their sensitive barbels.

 

[Avel1896]

Hi @Colin_T Up to what size gravel is suitable for cories?

 

[itiwhetu]

3-4 mm is what I use

 

[robmcd]

I have a small posse of c. sterbai in a densely planted tank with eco complete substrate, and have had zero issues. They have been thriving for over a year.

 

[Avel1896]

3-4 mm is what I use

Seems "big" to me.

 

[Avel1896]

I have a small posse of c. sterbai in a densely planted tank with eco complete substrate, and have had zero issues. They have been thriving for over a year.

Seems large and sharp to me. How are their barbels ?

 

[robmcd]

Seems large and sharp to me. How are their barbels ?

Just fine. Sterbai are on the smaller side as far as corydoras go (as far as the species that I have kept), so there isn't a lot of moving around of the substrate. Their barbels are intact and healthy looking. That being said it is densely planted with a thick carpet of monte carlo and staurogyne repens, so there are only a couple small areas of exposed substrate, but even as it was filling out everything was normal with them.

 

[itiwhetu]

I have said it before that the big issue with loss of Barbels is poor water conditions rather than the substrate. Corys hate Nitrates and if you do not have your tank very heavily planted you can very easily have a Niitrate level to high for Corys to be happy. It is not only about substrate.

 

[Avel1896]

I have said it before that the big issue with loss of Barbels is poor water conditions rather than the substrate. Corys hate Nitrates and if you do not have your tank very heavily planted you can very easily have a Niitrate level to high for Corys to be happy. It is not only about substrate.

I'm not sure Ian Fuller or @Byron agree with you about substrate.

Articles by Ian Fuller

Corydoras Articles by Ian Fuller

www.corydorasworld.com