Hi, I just remembered that congo tetra exist! I think it might be a good center fish for my tank since I want something very peaceful. In a 50 gallon would 6 congo tetra work with maybe 10 corydoras, 15 other smaller tetra, 5 otocinclus and maybe one bolivian ram ? I am not really good at knowing if something is overstocked/understocked and the bioload of a fish so that is why I am asking
Increase some of the numbers, otherwise no problem here. I checked back and this is a 4-foot tank, so a group of Congo Tetra would work very well. I would get 9-10, and roughly even male/female ratio (5m/5f, or 5m/4f). I have twice had this fish, once back in the 1980's with six in a 4-foot 50g, and more recently ten in a 4-foot 90g. The volume is not the issue, tank length is with this fish. They are not that rambunctious, though they do periodically like to have relay races where two males would seem to be having a race from end to end, taking turns leading.
Bolivian Ram is good; this will remain close to the substrate (they are substrate feeders), while Congo always remain mid-tank provided they have floating plants as they do not appreciate overhead light that much. My floaters needed thinning every 3 weeks to open up some surface space, and without fail the Congos would be lower in the water column for a few days following, until the plants had begun to grow back to cover the surface.
Other tetras are fine with Congo. I have never seen a Congo go after any other fish,but given their flowing fins (males) the other fish must be very peaceful and not in the slightest prone to fin nip.