I been bred 5 species of Polypterus till now and many people asked me which is the easiest and which is the hardest to breed and this is my answer.
First, i've been successfully breed fallow species without artificial hormone treatment.
Polypterus senegalus (CB Platinum X Nigerian WC, Nigerian WC X Nigerian WC)
Polypterus delhezi (Indonesian CB X Indonesian CB, Indonesian CB X WC, WC X WC)
Polypterus palmas "palmas" (WC X WC)
Polypterus mokelembembe (WC X WC)
Polypterus bichir (CB Nigerian X WC Koloton)
and also spawn of those species
Polypterus endlicheri (Indonesian CB X Indonesian CB)
Polypterus polli (WC X WC)
The easiest species to breed is P. senegalus as all know but it's only when the parents fish are CB.
Breeding with WC fish is much more complicate in every species.
If your parents fish are both CB, they will start breed naturally even in community tank if they are old enough and well cared enough
But with WC fish, you must be "Good enough" breeder and try everything, not just waiting for luck.
For hardest species, i don't think there is are hardest species to make spawn but just CB is easy and WC are hard if you don't use hormone injection.
If all are WC, they have quite similar difficulty but they just have different conditions by species.
The hardest species to raise them to breedable size and condition is Weeksii, Mokelembembe and retropinnis in my opinion.
Those three species will take very long to become mature. (Female mokelembembe i used for breeding was about 10 years old in my guess)
Hardest species to raise fry is all lower jaw species and mokelembembe.
Moke fry are even smaller than other bichir species and lower jaw species has too strong carnivores habit in juvenile species so they are hard to keep them in many numbers.
Hardest species to get a "Good one" was delhezi for me because it also require thremmatologyical technique.
So my recommend if you want to try to breed bichir for the first time, CB senegalus will be the easiest choice.
