I agree with Nutter, definitely sand. I started out with gravel and all my cories did all day was swim up and down the side of the tank. I switched to sand and they now spend most of their time sifting through the sand looking for food.
I think smooth, small river pebbles would be ok but not nearly as good as sand.
I am completely 100% for pebbles. Like the kind you buy in the bags at Petsmart. They are amazing and have tons of colors. I have two albino corys and 3 guppies. The guppies arent very particular, but my cory's love it! The cory's suck up a lot of sand when they clean the bottom making there digestive system a little screwy, haha. But the pebbles allow them to suck up the food easier between the cracks
I have small smooth pebbles, River pebble at the LFS. My emerald corys love it and they swim so smoothly over the pebbles and suck up the food in between. I used sand one time with a pleco when I had one of my first bettas and he sucked in so much sand i could see divids in it. I am a definate advocate for smooth pebbles for the corys.
Cories live over sand in thier natural environment. If you watch them carefully you will see most of the sand actually gets filtered back out through thier gills. This is thier natural way of finding food. The little bit of sand that is digested actually helps with the digestion processes. Sand that is aquarium safe & not so large that the fish can't poo it back out again never has & never will cause digestive problems withing any fish.
okay noted. I'll go with sand if that's the case for their natural habitat. I'm drawn towards darker coloured sand though.. Does that matter to the cories? Any idea if darker coloured sand is coarser or finer than light coloured sand?
I would go for sand everytime,has nutter said,cories sift sand through their gills,plus in between pebbles had harbour bacteria which if not cleaned regularly through vacuuming can lead to corys possibly getting bacterial infections.
My sand is kids play sand bought from argos in the uk
I'd agree with the information in that article except the not using black substrate bit. Most Fishlore members use Pool Filter Sand in thier tanks with a sand substrate. It's cheap, readily available & is'nt pure white. Playsand is acceptable so long as the grains are rounded rather than jagged but it's often pure white which coesn't look the greatest IMO. Eco-Complete or Flourite Sand are good for Cories. They are specific substrates for a planted aquarium & cost considerably more than most other substrate materials. They are both black but I've never heard of black being bad to have with Cories. They seem to like black just as much as any other colour. There is moonsand (I think that's what it's called) that is also very dark but I've never used it so I can't make recommendations about it.