Hobbyists who breed fishes seem to have not only infinite patience, but a tremendous sense of "what to do" in many situations. Of course, sometimes, you'll end up getting awesome results without knowing exactly why things worked!
Have you ever had this happen?:
You're working with a fish that you really wanted to breed, and you tried seemingly every way possible to induce it to do so, with no success?
You tried environmental manipulation, water changes, switching up pairs, playing with the day/night cycle, switching out foods, etc., etc., etc.
Like, it seems like you've tried everything.
Then, one day, sometime after you've thrown up your arms in defeat...BOOM!
You look into the tank they reside in, and...you have fry!
Ever had that happen?
It's one of the great mysteries of aquarium keeping...
And it's not a "bad" thing, of course.
The main "bummer" is that you often don't know what- if anything-that you did-or didn't do- was the "catalyst" for the spawning event!
It's like you're just scratching your head...
I think it just goes to show you that animals often defy our human-rationalized "processes" and do whatever they damn well please! I mean, you can do what "the books" say to get a fish to spawn, but unless the fish are up to it, you're just dreaming...
Or is there something else?
I have always felt- and still do- that one of the keys to getting our fishes to spawn is to examine the natural habitats from which they come. Not falling back on stuff like, "These guys need soft, acidic water..." or "Give them elevated water temperatures..."
Those are helpful, if not "generic" fixes. I can't help believe that so much more could be gained from really studying the habitats in which they evolved over eons.
Just doing a "deep dive" and thinking through the chemical/physical/structural aspects of their habitat can often yield some clues that you can utilize within the context of your aquarium in an attempt to get your fishes to spawn.
Obviously, this concept isn't "rocket science!"
As hobbyists, we've done research like this before and interpreted it in a way that works in aquariums. For example- annual killifishes and the use of egg incubation in peat moss- the key to closing the life cycle on that group of fishes. It's been done for many decades- a more-or-less perfectly accurate replication of the characteristics of their natural habitat, resulting in successful spawns.
Killies are a big success story! There are others, of course. Yet annual killifishes stand alone to me as an example of a group of fishes that we've literally replicated their natural habitats in order to facilitate spawning.
However, it seems that we are often "barking up the wrong tree" by engaging in tricks and hacks that are more "generic" than specific in nature. For example, what if there are seasonal water chemistry changes which occur in the fish's habitat, like a declining pH as a result of more leaves and such in the water at certain times of the year, or greater oxygen levels, more/less organics, or an influx of trace elements or other substances originating from water from overflowing streams?
Could we replicate this process by adding more botanicals to the water, utilizing a higher percentage of RO/DI water, etc.? Or, by slowing down water movement, changing the water chemistry in a given water exchange, etc?
Is this the right move?
Now, I realize that some of the fishes we keep have been bred in captivity for generations under dramatically different conditions than they have evolved under, so attempting to replicate the natural habitats- which your particular fishes may never have been exposed to-might seem a bit "excessive" or unnecessary to some.
That being said (and I've tossed this out before...)- do you really think that fishes have "evolved" so significantly in just a few generations that attempting to keep/spawn them in their wild environmental conditions would somehow be "detrimental" to them?
I don't think so, personally.
So, where does this leave us, the aquarists who dream of breeding "that" fish?
It leaves us doing exactly what we've done for decades- giving our fish the best food and environment possible, and hoping against hope that our husbandry decisions result in a spawn. And if they don't, we just have to either "stand down" on trying new stuff, or just keep on going.
However, I still think it's worth asking ourselves to consider the reasons why some fishes typically don't spawn in captivity...What is it- a single factor, or some combination of factors- which contribute to the spawning behaviors of our fishes?
Diet, temperature, water conditions, physical surroundings...all of these things are potential contributors to a fish's success in captivity.
We could dive deeper...
So what is it?
Why can't some fishes spawn in captivity- let alone, thrive?
What aspect of their habitat, or what physiological needs are you not currently meeting? Are their some sorts of microbial relations between the fishes and the water in which they reside? Osmotic pressures? Specific trace elements of compounds? "Stuff" which is lacking in a closed-system environment? Can we provide these things with some sort of "substitute?"
Are there diet-related issues- perhaps some specific vitamins or nutrients or other compounds which the fishes derive from particular foods- like insects- which are lacking in the foods we provide? Are there "intestinal infauna" within the gut of the fishes which are somehow not perpetuated in a captive environment?
Are probiotics an answer- a lead? Could it be that the fishes not being able to properly or fully process the compounds within their foods results in specific hormones (required to induce spawning) not being produced?
Is it some combination of these things? Is it perhaps some combination of water chemistry and the aforementioned bacteria, or...
Lots of interesting questions.
Well, would it be worth trying to replicate- as closely as possible, the specific environmental factors from which the fish hail?
I mean, I think so.
Would it be worth providing the fishes the exact foods found in their wild habitats?
I don't see why not!
Would it be necessary?
Maybe, for some fishes. Maybe there are specific nutrients present in their primary foods from their habitat which provide the specific nutrition needed to induce spawning?
I mean sure, you could "split hairs" and try to hunt down the specific insect or type of insect that your fish might consume in the African stream from where it comes. Or, more likely (and practically) perhaps a substitute from the same family. (i.e.; bloodworms for certain insects, or ants, etc...)
I suppose it's a matter of how far you want to take it!
The reality is, what makes the tropical fish hobby so enjoyable is that eternal quest for knowledge- the pursuit of a goal...And to unlock the secrets of those seldom, if ever captive-spawned fishes, that likely means going beyond the "brine shrimp- blackworms- and-water-exchange" thing.
It might involve that "deeper dive."
Asking seemingly fundamental questions...questions which, on the surface, it seems that we've sort of tackled before- but maybe not quite in as comprehensive a manner...
It might involve setting up and managing aquariums in ways we haven't even considered before. Accepting different functions, aesthetics, and applications in our tanks.
Frustrating though it may be at times, I don't think I know a hobbyist who would take up some other pursuit in its place, do you?
Didn't think so!
Keep striving. Keep trying...Keep "splitting hairs" as necessary...
Stay curious. Stay diligent. Stay resourceful. Stay persistent. Stay bold. Stay relentless...
And Stay Wet.