Apparently someone managed to trigger breeding in Mormyrids in 2020.

[RandomAlgae]

Intragenus F1-hybrids of African weakly electric fish (Mormyridae: Campylomormyrus tamandua ♂ × C. compressirostris ♀) are fertile - Journal of Comparative Physiology A

Hybridization is widespread in fish and constitutes an important mechanism in fish speciation. There is, however, little knowledge about hybridization in mormyrids. F1-interspecies hybrids between Campylomormyrus tamandua ♂ × C. compressirostris ♀ were investigated concerning: (1) fertility; (2)...

link.springer.com

This is great news, I hope more people would be breeding them especially Campylomormyrus tamandua, I love the color on these things.

maybe one day it would be common in the hobby.

 

[Ogertron3000]

An interesting thing to know, unfortunately even if they become common not many people will be able to keep them alive for long. From the hat I have seen they aren’t an easy fish for the average hobbyist to keep.

 

[Fallen_Leaves16]

Think there's a good few records of captive spawning in mormyrids; Aquarium-Glaser in Germany's offered farm-bred tamandua before, and I believe Mormyrus longirostris has been spawned with hormone tampering and whatnot.

Most mormyrids are reportedly quite aggressive (thus requiring large tanks or even ponds) and require rather substantial upkeep in terms of basic water quality and feeding before any spawning attempt can be made in the first place. Interestingly enough, the paper seems to suggest that a dense group of sexually-mature specimens are able to co-exist in a relatively small tank, and spawn to boot, somewhat contradictory to what Aquarium-Glaser suggests.

 

[Ansorgii]

I wouldn't blindly trust Glaser, not saying that they do bad research, but fish arent as consistant as math and everyone interprets their experience differently. And what kind of commercial breeder gives his secrets away for free ?

Some of their older posts have not aged that well, back then people just didn't know and so did they.

 

[Joshuakahan]

An interesting thing to know, unfortunately even if they become common not many people will be able to keep them alive for long. From the hat I have seen they aren’t an easy fish for the average hobbyist to keep.

I haven’t had much luck with them, but the last one I tried was some type of elephant nose over 20 years ago.

 

[Fallen_Leaves16]

Turns out many more mormyrid species are routinely spawned in laboratory settings. Was internet browsing for info about spawning various knifefishes (as it has often been mentioned that many spawning reports exist, and some mentions of hobbyists breeding up to a dozen different species sometimes circulate the internet), and came across a few studies comparing larval development of mormyrids and gymnotiformes, where anywhere from four to six different species were spawned (one study mentioned breeding F1 and F2 offspring), not including C. tamandua, though a few other Campylomormyrus spp. were popular candidates for such studies.
Here's one such study (can't find the other two I looked at):

https://www.sciencedirect.com/science/article/abs/pii/S0928425703000111

Unfortunately, practically all of these studies were stuck behind a paywall, and therefore spawning details for mormyrids were unavailable.

On a side note, I was able to discern that Brachyhypopomus and Eigenmannia, amongst other knifefish species, only required a drop in conductivity to trigger spawning (potential breeding project? ). Also, Gymnotus carapo is apparently a mouthbrooder, not a territorial nest-guarder, which I found rather interesting.

I would assume mormyrids to require a drop in conductivity to trigger a spawn, much like many other fishes, and merely require proper conditioning beforehand. They may be seasonal breeders, however.

I suppose it shouldn't be too unexpected; electric fishes are, after all, quite frequently studied for scientific purposes, and it should be inevitable that spawning records would exist after some time.

 

[Milingu]

Very interesting read. Especially the conditions:

"2.3. Environmental factors
The variation of environmental factors leading to
gonad maturation comprised: decrease of conductivity,
increase of water level and imitation of rain.Decrease of
conductivity (this in general leads to pH decrease as
well) were achieved by adding demineralized water
either continuously of three times per week to the water
in the experimental tanks.This manipulation also led to
water level increase if no overflow system was installed.
Imitation of rain was performed by spraying fine jets of
water onto the water surface by using a re-circulation
pump.Details of the method are found in Refs. [22,23]
and [44].Photoperiod was held constant (light/dark
12:12) and temperature ranged between 25 and 30 C.
Egg incubation and embryological development took
place at 26–28 C."