Livebearer cycle? Hypothetical scenario?

[ichthyogeek]

So I was browsing through WWM's online magazine articles, and clicked on the livebearer article "Fantastic Four Livebearers." Two fish caught my interest: the Poecilia velifera-the Giant Sailfin Molly and Belonesox belizianus-the pike livebearer. According to the article, they both have very similar water parameter requirements (pH 8.0, 20-30 dH, 25-28 C, and require brackish water. The molly gets to 6-7 inches, while the pike livebearer gets to typically 4-6 inches, with males being on the smaller size, and females being bigger. The pike prefers to eat small fish for a diet, while the molly is an herbivore. I'm not making a tank for these fish, but this is just an idea that popped into my mind that I was wondering if y'all would mind commenting on.

100 gallon livebearer aquarium, because 55 and 75 gallons seem too small for such big fish.
Calcium carbonate sand substrate to keep the pH buffered and the dH up.
Anubias, Java Fern, and dwarf sagittaria as plants, with the Anubias and Java Fern attached to limestone, and the dwarf sag acting as a carpet plant.
2M:2F Pike livebearers
2M:6F mollies
3M:12F "feeder" guppies separated in an eggcrate container, or walled off via eggcrate

The Pike livebearers would mostly be the showcase fish, with the mollies acting like...well, food factories. The mollies would produce fry that would then be eaten by the pikes, whose fry would subsist off of guppy fry. Any guppy fry that survived to adulthood that were male would be fed to the pikes, while females would add to the population. I use the term "feeder" guppies because the colorful guppies that I see at Petsmart and Petco aren't hardy enough. So, what do y'all think?

 

[ichthyogeek]

Nobody, anybody?


Sent from my iPhone using MonsterAquariaNetwork app

 

[duanes]

The mollies are a great fish on their own, I have snorkeled with them in the cenotes of Mexico, where they share habitat with Rhamdia catfish, and Rocio (JDs).
Large dominant males easily reach 7", and are amazingly beautiful, and hold large, sunlit, algae covered rock territories as deep as 15 to 20 feet.
Although I have not kept Belonesox, I have heard its difficult to keep more than 1 to a tank, as they tend to kill each other. This may be because most tanks they are kept in by live bearer keepers, are often too small. Your 100 may be an exception.
Below is a video I took in Eden Cenote, where velifora mollies are everywhere, although at the time of the shooting none of the really large ones were seen.
https://www.youtube.com/watch?v=txmi1mng_XQ

 

[ichthyogeek]

duanes, approximately how much territory did the velifera control per male in Eden Cenote? Also, do you happen to know the parameters of the water there?

 

[MN_Rebel]

The reason why pikes kill each other isn't because the tank is too small but because the females are always bigger than the males and the females are highly cannibalistic. A single large female pike can easily wipe out all guppy populations and majority of molly populations with only large male molly left in your 100 gal.

 

[duanes]

These full grown large molly males would control a boulder about the size of a VW Beetle, and seemed to be bathed in full sunlight for a long period of time.
These were giant full bodied males of 7" and would be surrounded by many females, but chase off all interlopers. They would also defend the area against full grown JDs.
Below are shots from Cenote Cristalino, where I found a similar scenario.

 

[joe jaskot]

You need a lot of live food to keep the pike livebearers. If not fed enough, the female will eat the male. Tough fish to keep over the long haul. Not easy raising the fry due to the amount of live food needed. The bigger fry will eat the smaller fry.

 

[ichthyogeek]

MN_rebel: Even though the chosen molly species is bigger than the pike in adulthood, and the guppies will be separated? Still, I may have to revise it to 1M: 1F. You seem to have experience, so are there any sex-aggression issues between pike livebearers in regards to sex ratios? I know that mollies, platies, and guppies should all have higher female to male ratios due to males being incredibly promiscuous, but since female pikes are so carnivorous, will that deter all but the bravest males?

duanes: Wow!!!

joe jaskot: The whole point of having several large mollies and a colony of guppies is to supplement the pikes diet. I'm hoping that the multiple, multiple spawns of guppies and mollies that get dropped in the tank can either fully sustain, or at least partially sustain the pikes. Assuming that each female fish gives birth every 30 days, then I can count on a molly fry spawn every 5 days, and a guppy fry spawn every 2.5 days. Let's say that each fish drops upwards of 20 fry/spawn. That's enough to feed each pike livebearer with 1 molly fry and 2-3 guppy fry per day. Of course, most spawns after livebearers reach adulthood, can number up to the hundreds. The only problems I'll have, are making sure the initial populations of guppies and mollies stay stable. Afterwards, I should only have to feed the mollies and guppies. Unless I did my math wrong...

 

[MN_Rebel]

These pikes are greedy predators and a mature female pike can easily wipe out the entire guppy population in just less than a hour. After all these pike livebearers don't have any problems with eating feeder goldfish and red rosies. They won't have any problem with eating molly females and smaller males. These female pikes can get bigger than 8" and a 10" pike livebearer were reported. I am afraid that it will leave you with just a happy fat pike and possibly a large scarred males molly that survived a maul attack.

 

[ichthyogeek]

But aren't feeder goldfish and red rosies small fish? I'll admit to not ever keeping predatory fish of any kind, so unless I'm mistaken, how would a 10" pike eat a 7" molly?