Marty has been a tropical fish hobbyist most of his life. He has kept Endlers since February of 2013.
Male adult pure Endlers are all generally the same size—reaching a length of approximately 3/4"–1" long. They will usually have a somewhat long slender body and bright coloration.
Pure adult female Endlers average approximately 1-1/4" to 2", however, we have on occasion seen them grow to nearly 2-1/2" to 3" in very large aquariums under ideal conditions.
Because hybrid Endlers are often hybridized with guppies, their size can be influenced by the guppy genes.
Hybrid Endlers tend to be larger and stockier than their pure counterparts, especially the males. Hybrid female Endlers can be difficult to distinguish from pure female Endlers.
Although hybrid Endlers tend to be larger, size and shape are cannot be used to ensure that Endlers are pure. There are many hybrid strains that are nearly identical in size and shape when compared to pure Endlers.
How Fast Do They Grow?
Each Endler and Endler hybrid strain develops at a slightly different rate. Water temperature, water conditions, food, and lighting can all affect the growth rate of Endlers.
The higher the water temperature the faster the Endlers will grow however higher temperatures can also shorten the lifespan of Endlers.
In general, they should be a nice size when they are about 6–8 weeks old. You can usually determine the sex of the male Endler at the age of 4–6 weeks old as the gonopodium develops. With some experience, you may be able to determine the sex of an Endler at an earlier age.
Male Endlers from strains that have black markings will often develop small black patches early in their development making it relatively easy to spot young males at an early age.
The development of the coloration varies depending on the strain however the black markings usually show up first and can be the first indications that an Endler is male other than the gonopodium.
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Most female Endlers have little to no coloration but usually grow larger than male Endlers.
Watch Out for Less Colorful Males
From time to time a male with little or no coloration may be produced within a colony. It is important to remove these males from the colony as soon as possible as they can cause the overall colors of your colony to become less colorful if they are allowed to breed.
Due to their lack of coloration, these males can be difficult to spot especially in a crowded aquarium. Look for the gonopodium, a male sex organ that develops from the anal fin.
How Soon Can the Females Become Pregnant?
Under ideal conditions, breeding stock should be selected from virgin females and select males. The stock should be selected for the physical characteristics that want to carry on to your future stock. Not only should fish be selected based on their colors and patterns but also on their body size and shape as well as health and vigor.
Trying to separate female virgin Endlers can be somewhat of a challenge as the females can become pregnant between 4 and 6 weeks old. If you have room for extra aquariums, breaking up the fry into small groups will make it easier to obtain virgin females for breeding.
Because the males all develop at different rates it is easiest to remove the males as they are found and place them in a grow-out tank.
Selecting breeding stock from your males should be done after they are around one year old. It will take nearly a year for the males to reach their full color and pattern potential.
Endlers Are Ideal for Small Spaces
Due to their small size and because they will use all levels of an aquarium, they are ideal for those who have limited space for an aquarium. They should be kept in a tank that is at least 10 gallons.
Because Endlers breed readily, those who have limited space for a fish tank should only keep male Endlers so that the aquarium doesn't get too crowded over time.
Keeping males and females together in one tank can quickly lead to overcrowded conditions that can be unhealthy to your Endlers.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2021 Marty Andersen