Questions regarding cory breeding

[Goggy]

I am receiving a group of corydoras eques, 2 females 4 males and intend to breed them.

I have bred cories before, but have always used:
- sand as a substrate
- a jar with an airstone to hold the babies
- a hang-on-back filter

After doing lots of research, I learned that cories sometimes bury their eggs in the sand which makes you unable to obtain the eggs amongst all the grains. I figured if I remove sand and go bare bottom, the cories will be forced to lay their eggs in visible areas where I can retrieve them. My question is by removing sand, does it have any effect cory breeding?

I would like to switch from a jar with an airstone to a net/plastic breeder box that hangs on the aquarium side as it seems easier. Are there any disadvantages to this?

I only see videos where the cory breeder fishtanks have a sponge filter. Is there any specific advantage to this or are they just used as they are the most cheap?

I have 2 cycled and ready tanks, one bare-bottom and the other with sand, but both with HOB filters. So if I need a sponge filter I plan to just set one up in the tank and let it run alongside the HOB filter until it becomes established

 

[Gourami36]

I’m pretty sure they do not bury their eggs. Bare bottom can damage their barbels.

 

[Byron]

Agree. So far as I know, all species of cory deposit their eggs individually on a surface. They are sticky and tend to adhere well.

Bare bottom tanks are not healthy and they are a greater risk for fish because there is no "bed" for the various species of bacteria that colonize the substrate. The substrate is the foundation of a healthy biological system. Now, having said that, there are breeders that raise fry in no-substrate tanks, but they also do frequent water changes to remove the detritus that accumulates, but also just to freshen the water which is more in need of this without the substrate because those essential bacteria have no place to live. The filter is not the same as a substrate.

The other thing with cories is their natural feeding behaviour; they sift mouthfuls of sand, expelling it out the gills. No sand substrate will stress them out; they expect it to be there.

To the sponge filter question...these are usual in breeding and fry tanks because they provide incredibly good biological filtration and are not dangerous to eggs or fry. Neither can get sucked into the filter.

I am not a breeder per say; I have cory fry that appear but I do not do any large-scale breeding. I have used one of the fry nets inside the main aquarium in which to raise the fry and that had benefits like identical water parameters, water flow and temperature stability, but it might not be practical for more serious breeding. I have also raised fry (that I have recovered when cleaning the canister filter) in my 10g tank which houses a group of pygmy cories that spawn regularly. The cory fry were able to grow up without fear of predation, and then were moved into the main tank to join their elders.