Thoughts on Breeding Mosquitofish - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 1 Old 09-14-2011, 09:37 PM Thread Starter
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Thoughts on Breeding Mosquitofish

I know, they're not cute, and even heard a few people refer to them as the "ill-tempered guppy-like things." However, I have found the species Gambusia holbrooki rather fascinating. I will make it known that yes, I do have some breeding at this very moment in the tank indiscriminately - but the sort of breeding I'm interested in would be for particular traits.

Tank Size:
In a few weeks I will purchase a larger tank (to move the other fish I have into) and will have a 10 gal tank in which to keep the Gambasia in. I was thinking about setting up a divider, with males on one side and females on the other, and breeding boxes. I have a 2 gal tank in which I would keep the resultant fry.

The temperature would be kept within optimal range for breeding (about 80 to 85*F), although they can tolerate higher and lower temperatures.

Specific Species:
Eastern Mosquitofish (Gambusia holbrooki)

They seem to breed readily regardless of the substrate as they are live-bearers. I was thinking of using sand in the smaller 2 gal tank for the fry - in order to avoid mishaps in which a baby fish becomes wedged under rocks (rare, but happens). Plants would be used for both adults and fry.

I have a regular "Hang On the Back" filter, in which it siphons up the water then pushes it through two filters and then pours out the front like a tiny waterfall. Perhaps not the most efficient system out there, but for Gambusia, it should be sufficient. The filter is turned off at night.

As for the fry, the tank wouldn't have a filter. Rather frequent water changes would suffice. They are a species of fish that thrives in stagnant water, so I would imagine the demands in regard to their care would be minimal.

Lighting and when used or not used:
Aquarium light bulbs recommended for aquarium plants will be used. The lights are turned on about 8 am and turned off about 8 pm.

Food used for conditioning:
Nothing exceptional, simply tropical flake food, algae, and edible plants.

Food used for fry and at what stages which food was used:
This seems a tad more tricky. I was thinking of using algae, edible plants, and perhaps powered flake food. Might even cultivate some daphnia and similar critters to suit their palate.

Water change frequency and what type of water:
I change 25% of the water every week with a 10 gal tank, and then an entire water change once a month.

With a 2 gal tank, I would change 25% of the water every couple of days.

The water would be from the tap combined with AquaSafe Water Conditioner with BioExtract. The pH and water hardness resembles that found in the local lakes and streams from which these fish have been collected from. Although, once again, this species can tolerate variation.

Additional Information:

What would I do with the resultant offspring?
  • If the fish have desirable traits, they will eventually find their way to the breeding tank and matched with a fish with similar desired traits.
  • If the fish do not have desirable traits, or are born deformed, then they will become feeder fish for fish in the larger aquarium. If deformities continue to arise from a particular pedigree, then breeding for those particular traits will most likely be discouraged or an infusion of new bloodlines will be used to add variation back into the gene pool.
What will I not do with the resultant offspring?
  • I will not release them back into the wild. I intend to alter these fish in ways that might make them susceptible to native diseases which when bred back into the wild population could weaken existing wild populations or these alterations could make them more virulent due to changes in physical form, temperament, breeding requirements, diet, etc.
  • I am not heartless, as I do grow to admire the fish I keep, but at the same time, I'm not foolish. Endangering an indigenous species, even with an altered variation of the same species isn't worth the value of a few fish.
  • I have no intention of hybridizing this species with another. Keeping a species "pure" that is captive bred doesn't really matter much to me, since I consider any alteration to an animal by humans to be artificial anyway. I would rather avoid the unforeseen difficulties of trying to isolate desirable and undesirable traits through tracing back and forth between one species and the other. Gambusia holbrooki is a very successful species, I would imagine it has quite enough variation to tinker with in its own gene pool.
What are some traits I hope to breed for?

This has yet to be fully speculated about. However, I have noticed some of the fish are darker than others while others are of a lighter variation - regardless of being male or female. I've noticed some males are more aggressive than others, whereas others are simply more curious and confident. There will probably be overall size differences from the established norm for males and females.

So far, I could try to enhance such traits as:
  • Color - lighter or darker
  • Temperament - aggressive, meek, curious, or gentle
  • Size - larger or smaller adult size than is normal for the species
Difficult traits I could breed for should I continue this hobby in the coming years:
  • Modification of fins
  • Color variants - muted or excessively colorful
  • Increasing hardiness (although I'm not sure I could improve on what nature has perfected)
  • Alter body shape - shorter or longer


Any suggestions, advice, and words of wisdom would be greatly appreciated.
Serico is offline  

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