How to breed Biotoecus opercularis

biotoecus opercularis breed ph GH TDS RO

How to breed Biotoecus opercularis

May 16, 2021

I would like to summarize what I have learned from my experience in breeding Biotoecus opercularis.

(Biotoecus opercularis is called “Green dwarf cichlid” in Japan.)

I haven’t found an article about this fish breeding so far, so I hope this article will be usher in discussion and further information sharing.


  1. Raising parent fish in good health
  2. Creating a suitable environment for breeding
  3. Spawning → hatching
  4. Raising a child (F1) in good health
  5. Growing that F1 can give birth to F2

Strictly speaking, it may be said that I achieved the above (5) and succeeded in breeding, but it seems that it will take more time until (5), so I will write about (1) to (4).

It will be a long article, so you can jump to the chapters on this page from the list of contents below.



Environment suitable for breeding

First of all, this fish

Very sensitive to water quality (especially total hardness)

That is the biggest breeding point.

In bullet points,

  • Maintaining a stable total hardness (GH) of 2.0 ゚dH
  • Maintaining a stable pH of 5.0 to 6.0
  • Maintaining a stable water temperature of 25.0 to 26.0 ℃
  • No ammonia and nitrite detected
  • Stable maintenance of low nitrate concentration (10mg/L or less, preferably 0mg/L)
  • The water flow is very weak, but the water stagnation area should not be created
  • Breeding density is up to 2 pairs in the case of a 60cm standard aquarium
  • Food should be digestible (without flour) 1-2 times a day
  • It doesn’t matter if the fish is thin or overweight
  • Increase the number of places (driftwood and aquatic plants) where fish can be hidden
  • Lights should be weak
  • Spread a thin layer of fine sand on the bottom

It will be as above.

I will explain the key points in order.

Total hardness

Long-term breeding is possible if the total hardness is in the range of 1.5 to 2.5 ゚dH.

In an environment of 1.0 ゚dH or less or 3.0 ゚dH or more, the movement becomes sluggish and the food intake is slightly reduced, making long-term breeding difficult.

There is information such as GH=0, TDS=0 for the local water quality,

It is only that the value cannot be measured with the reagent or test device, and as long as it is a living creature, it is impossible to live with completely zero minerals.

Therefore, it cannot be bred only with RO water (GH=0, TDS=0).

The right amount of minerals (= osmotic pressure) is required.

In water with extremely low mineral concentrations, fish temporarily maintain their lives by using the minerals in their bones and muscles, but weaken in the long term.


The ideal pH is 5.0-6.0.

I use “Sera Super Peat” or “Eheim Torf Pellet” to lower the pH.

The amount used depends on the pH, KH, etc. of the original water, so try several times to find the appropriate amount.

Nitrate concentration

Biotoecus opercularis are fish that are sensitive to the harmful effects of nitrates (NO3), so it is necessary to manage them to 10mg/L or less, preferably 0mg/L.

I change the water with a total hardness of 2.0 ゚dH, and in my case, I also use denitrification to keep the nitrate concentration at almost 0mg/L.

I make anaerobic filtration work by inserting a filter medium called “Seachem Matrix” into an external filter.


Lighting is not required, but it would be better if you had the brightness needed to observe the condition of the fish.

Therefore, if you want to put aquatic plants, Borbitis or Microsorum is recommended.

Bottom sand

Like the genus Apistogramma, Biotoecus opercularis inhales food along with the sand and exhales only the sand from the gills, so you need to use fine bottom sand with rounded edges.

The reason for thinning the bottom sand is to prevent the sand from becoming a water stagnation.

Spawning substrate

Biotoecus opercularis are cave spawners.

There is no problem with so-called “palm fruit shelters” or broken flower pots.

Aquarium blindfold

Only in the Biotoecus opercularis aquarium, I put thin PVC boards (like underlays) on all three sides (both sides and back) except the front side of the aquarium so as not to surprise the fish as much as possible.

I’ve never removed this board, so I don’t know the difference between its presence and absence, but it’s better than nothing.


Parental nature and pair bond

I think there is a big difference in the alertness and stress of females when males become enemies and allies of females after spawning and hatching.

I feel that this is the point of whether parents can protect the fry that they have swam, or if they cannot protect it, they will eat it.

This is not limited to Biotoecus opercularis, but it is said that there is a difference in fertility after becoming an adulthood between artificially hatched fry and parent-raised fry.

In other words, it seems that fry bleeding by artificial hatching do not know the affection of their parents, so they do not lay eggs even when they become adults, or even if they lay eggs, they do not succeed afterwards.

However, on the contrary, I heard that it is more difficult to breed wild pairs, so if you are trying for the first time, it may be better to start with “parent-raised (F1)”.

Furthermore, I learned this from comments from overseas people,

The survival rate maybe low because if the parents are close relatives (purchased at the same time in one place).

There is also information about it, so it seems necessary to devise a way to combine male and female.

Personally, the breeding of the genus Apistogramma is not very thorough,

but I’ve heard some cases where the survival rate of fry was higher when pairing with an individual that was handed over from another person instead of killing one after purchasing the genus Apistogramma as a pair.

This is also

Not “close relatives”

in that sense, it may be a credible story.


After spawning

In most cases, spawning takes place at night.

Therefore, it is common that when I woke up in the morning and looked at it, it was laying eggs.

Whether or not the lights are turned on as usual is different for each person who has experienced it, but I try not to turn it on at home.

I don’t think he would bother to lay eggs in a bright place in the natural environment, and in fact, when the lights are turned on, female is more alert to the surroundings, so it is better to darken.

It takes about 5 to 7 days from spawning to hatching, depending on the water temperature.


It is okay to change the water until it hatches.

Of course, it is not good to add water roughly, but

softer than usual,

there is no problem if you do it.

The female is not afraid of anything while protecting the egg.


After hatching

After hatching, the female will be in “super-high alert mode”.

Of course, changing water is strictly prohibited.

It’s also not good to slap near the aquarium.

It is okay to turn on the lights temporarily.

(The video I’m posting on YouTube is shot with the lights on.)

Also, even cautious parents eat food, so give it as usual.

Then, prepare for the brine shrimp hatching when the fry Yorksack is gone.


Fry food

The fry food is given as follows.

  • Brine shrimp (live food)
  • Shellless Brine Shrimp Artemia
  • Ultra-fine artificial food

However, the Salt Lake brine shrimp is too big to eat, so I will use the one from Vietnam.

If possible, give 4 times a day (every 6 hours).

Twice a day (every 12 hours) it’s fine, but the survival rate is reduced.


Closing words …

Formerly known as the “phantom jewel of the Amazon River”, I’ve only seen it in photographs, and I can’t forget the surprise when I saw the real thing (swimming in an aquarium) a few years ago.

At first glance, it looks like a translucent fish, but the blue glow when the water quality matches perfectly is a very attractive fish with something special.

Although it is a fish that is challenging to breed, including its sensitivity to water quality, the joy of achieving it is beyond description.

Recently, it has been imported about twice a year, and the price has settled down to an affordable level.

I don’t really agree with raising wild fish with ease, but if you really want to try it, I would like you to take on the challenge.

I hope this article has helped you.