Mosquitofish/Gambusia as live feeders?

[THQ]

Hi all, I live next to a brackish estuarine river full of these critters. I tested the water with a hydrometer and it actually has a specific gravity of 1.030, which is basically seawater. I understand these guys are euryhaline (can comfortably live from freshwater to full marine and everything in between).

I know that as a general rule, wild caught live feeders are probably a bad idea as they carry parasites. But in my unique situation, I would think that whatever parasites they carry, must be adapted to high salinity, so when I drop them into my fully freshwater tank, they will die off and they fish basically self-cleanse. Same reason why there is no overlap between any pathogens in the freshwater vs marine aquariums.

As they have lived in seawater all their lives I doubt they will survive a few weeks in a freshwater quarantine tank. I'm not keen on convering my QT to marine, as it means it will destroy my freshwater bio filter and I need to re-cycle.

What are people's opinion on this? On one hand I've heard people feeding thousands of these per week to their monster fish for years without any problems. On the other hand I've heard of a few people losing fish from parasites carried in the mosquitofish.

Thanks.

 

[Hendre]

Tbh I think you need to make a salt qt, the change will shock the fish as much as the parasites and if it is internal parasites water salinity change won't affect them quickly.

 

[Bottomfeeder]

Mosquitofish, as a species, make fantastic feeders. They are nutritious and don't contain the high thiaminase content that goldfish and minnows do. However, there is always a risk of introducing pathogens and parasites when you're catching your own feeders. The best way to go about having a steady supply of mosquitofish would be to start a colony... catch a good amount of males and a good amount of females, and put them in a big tank together. A quarantine period of at least a few months would be necessary to hopefully purge the parasite load from their system, but if they clear the quarantine period, they'll be good to go.

They breed like rabbits. Just don't use a power filter, because it will suck up the fry. Mosquitofish fry are an impressive size at birth, but you will need to add some cover to the tank (they really like floating mats of plants) to prevent the adults from eating them.

The only missing piece here is the species you're working with. You said they're in sea water, but you didn't give their location. There are species of Gambusia that live specifically in estuaries and even coastal regions, but many freshwater species can live in marine environments as well. I'm not sure if you can convert the marine species to full freshwater, but you could definitely lower the salt levels over time so they're better for freshwater predators.

If you could provide the geographical location in which you're working, and possibly a picture, we might be able to figure it out.

 

[Wailua Boy]

Gambusia are slightly harder to breed than other livebearers, mainly due to their aggressiveness to fry but nonetheless they are fairly easy to culture. I would agree as previously stated, they will need a full quarantine period.

 

[Wailua Boy]

Post a pic of fish if possible, I'm curious what species it is.

 

[MN_Rebel]

You're better off with breeding guppies or just catching mosquitofish to restock the feeder tank. Gambusia species are highly predatory to their own fry and they're difficult to culture in glass tanks unless you have a large tub or a goldfish pond.