Zoogoneticus tequila, English version

They come from central Mexico, the females are assertive, powerful and the males desire and fear them. The males are handsome, aggressive but cannot avoid being controlled by the females which henpeck them mercilessly. I'm not referring in these lines to the plot Mexico's latest soap, but the behavior of the viviparous Mexican fish Zoogoneticus tequila.

The Zoogoneticus tequila is known in English as the "Crescent Goodeid" due to the coloration of the tail fin of the male or the "Tequila splitfin" in recognition of the anatomy of the anal fin of fish in the Goodeidae family. I don't know if it has been awarded a common name in Spanish as it is not available locally in the commercial aquarium trade but in this article it will be called the Tequila. The Tequila nickname refers to a volcano in the vicinity of its natural habitat. Fish of the Goodeidae family are distinguished by a number of fascinating biological and anatomical adaptations that separate them from other livebearers, these make them an interesting subject for the aquarist. Their behavior is also of interest because unlike other viviparous fished Zoogoneticus interacts with other fish in the same way that Mike Tyson interacted with Evander Hollyfield's ear in that unforgetable fight.
We will start by detailing the reproductive adaptations of this species. The male fish of the family Goodeidae lack a gonopodium, this immediately distinguishes Zoogoneticus from other viviparous fish common in the market such as guppies, swordtails and mollies. Because they have no specialized structure such as the gonopodium, males use the first few anal fin spines to transfer sperm to the female. The females do not store sperm so they have to be fertilized every time they produce a litter, in this respect they are unlike the Poeciliae such as guppies and mollies. The young develop inside the female and produce a structure called trophotaenia which comes out of their bellies and allow them to absorb nutrients from the mother's body. The females produce relatively few offspring compared with other livebearers, 10 to 15, but the young are much larger than usual in viviparous fish. The attitude of adults towards the young is similar the way Herod treated his own children. Adults actively hunt the young, they should be separated from them so they can survive. It is reported that the female gives birth roughly every two months.

Some species of the genus Zoogoneticus seem to have very restricted geographic distributions. Tequila has not been collected in the wild since 1990 and it is suspected it might have become extinct in the wild. Tequila was recognized as a new species in 1998 even though specimens had been collected since 1955. The species Tequila is related very closely with Zoogoneticus quitzeoensis described in 1898 and Zoo. purhepechus a new species described in 2008. Its origin lie in the state of Jalisco, in the river Teuchitlan.

Males are grayish, some scales of the sides of the body show a pink iridicensce. The females are generally gray but the ones I have show a fairly dark color probably because the level of illumination in their aquarium is low. My fish are still young so it is likely they will continue to change color as they mature.

I keep the fish in a tank 30 gallon long. The water in the tank has a pH of 7. The tank has no conventional ornaments. The bottom is covered with teak leaf litter, a soft mud that has resulted from the decomposition of the leaves and algae that has covered the remains of the leaves. Laying just below the water surface is a mass of plants, mainly Hygrophyla difformis. The temperature of the tank varies between 70F and 80F. I change about 80% of the tank water every two weeks.

The fish are fed three times a day, in the morning when I go to work, noon and in the evening just before sunset. If anything can be said of these fish is they eat everything I offer with a breathtaking lack of discriminating criteria. The cheapest flake food is eaten with the same zeal as the mosquito larvae,"bloodworms" and food pellets. I try to vary the diet a bit every day and while some days I give them bits of minced shrimp in others I give pellets. Different sources recommended that these fish should be fed with a vegetable-based food. But as the tank has a good growth of algae, I have not bothered to give any special vegetable based food.

In the beginning there were five Tequila in the tank, three females and two males. But the two largest females harassed the younger in a manner so barbarous I suspect it was killed or that it may have jumped from the tank as it disappeared a few days after they arrived at my home. This is illustrative of the character of this species. They are aggressive fish, truculent and lacking in subtlety. In short they have an horror of a personality. In this they are the veritable antithesis of the ideal fish we want in a community tank.

Tequila breeders recommended keeping this species in a species only aquarium. During a normal day the largest male harrases several times the smaller one. Males approach females with caution since unreceptive females can bite. Not a day has passed without seeing that a Tequila has lost a scale here or there or has a bite in one fin.

What role can play in our aquarium a fish with so abhorrent a personality?. It turns out that the inclination for discord and contention of this fish makes it perfect for aquariums with small cichlids of like personality. But its role is not simply to share the aquarium, the Tequila with their challenging personality can provide a distraction for the cichlids. By diverting the attention of the cichlids they can ameliorate in a small degree intraspecific aggression and when the reproduction of the cichlids occurs, the Tequila become a catalyst for the protective instincts of the cichlids toward their young.

My Tequila share a tank with five jewelfish juveniles, Hemichromis lifalili, a jewelfish from Congo or Zaire. The lifalili are famous for two reasons, one is that when breeding they develop one of the most spectacularly colorful nuptial dress of any freshwater fish. The other is their unfortunate tendency to murder, in a violent and bloody way, all the other fish when they have young to protect.

Even when they are young and small the lifalili are far from being like Mother Teresa and they spend a lot of time chasing and attacking each other. Sometimes they harass the Tequila in an absent minded sort of tokenish way, they reserve their worst venom for their own kind. So far as I can tell, I have not noticed that any lifalili has caused any apreciable harm to the Tequila, to the contrary, subdominant lifalili often spend much time hiding in the vegetation along with the long suffering Tequila males.

You should realize that in spite of what I recommend above, you can't drop the Tequila in a tank with cichlids and expect everything to be peaches and cream. Nothing can be further from the truth! There is no faster way to kill a Tequila that throwing it in a aquariun where some territorial cichlids are tending their fry. The Tequila should be housed with the cichlids when the cichlids are still young and in a aquarium large enough for them to escape the aggression of cichlids. But that is another theme and in the future I will dedicate an article to commenting it.

The Tequila are very alert of my presence near the tank and watch me intently when I sit down to look at them. They are less shy than the cichlids and are not intimidated when I approach with a camera. Every day I spend some time observing them and the fish have learned that when I arrive in the afternoon there will be a special treat. So when I sit next to the aquarium just before night fall they react with great excitement. They are so bold that I've seen the whisk away a piece of shrimp from a cichlid with such speed that the cichlid is left wondering what happened.

The Tequila eventually will be moved to their own tank as the adults lifalili reach a size of about six inches and even before reaching this size they become a mortal danger to the other fish when they have a school of young to protect.

As you have seen the fish Tequila are not for everyone. But they have a certain charm, in an horribly obnoxious way, that transcends the absence of bright colors and peaceful behavior