While without a picture no one can readily ID your fish, I would be willing to bet almost anything that they are NOT guppies.

If I had to venture a guess, I'd say Mosquito Fish, which are frequently introduced into manmade bodies of water to help control the larvae of the very pest they're named after. Mosquito Fish are virtually identical to female guppies in size & appearance, the only difference being that the male does not develop a male guppy's colors, but stays the same greyish color as a common female guppy. Since Mosquito Fish are livebearers just like guppies, the males do have a gonopodium.

My vote is for Mosquito Fish.

Interesting, I have seen pictures of other plain guppies and they look the same...people have suggested that someone probably dumped their aquarium in the lake and that's how they got there...I posted a picture in the Gallery of a female and a male...it's not a great pic, but hopefully a good enough one to be useful in identification...see what you think.

Checked your gallery photo Marisho & those are definitely Mosquito Fish. You'll find that they behave & breed similar to guppies & other livebearers; they just don't have the color or finnage.

Like I said, they're purposely introduced to manmade lakes & farm ponds all over the country for mosquito larva control - especially since West Nile Virus started raising its ugly head.

WOW! It's so funny, because I sent the SAME picture to the guy at Guppyplace.com and he said they WERE guppies. You've piqued my curiosity tho, so I am gonna go research mosquito fish....thank you very much!

Did some research. Viewed some pictures. Seems I have a tank of mosquito fish. It was bad enough that they were guppies and not trout...now they are a species of fish that people refer to as "The Fish Killer."

Ugh.

I've never heard them referred to as that. In fact, their lust for mosquito larvae & peaceful nature is one of the reasons they're used as often as they are.

Where did you hear this & what is the reasoning behind it, if you don't mind my asking?

I have a link to a site on the control of Gambusia where I read that they are referred to as: "Gambusia holbrooki, the "fish destroyer.""

The first link is the first site where I learned about them and the second is where they are referred to as fish destroyers.

http://www.mosquito-kill-net.com/mosquito-fish.html

http://www.gambusia.net/

Thanks for the site info - interesting stuff!!!

But at least they're not "fish killers" in the sense that they're aggressive. They "kill" by eating native fish eggs & fry, same as the goldfish that people love to dump into ponds when they grow too big.

Still a problem, no matter how you look at it. It's a shame that West Nile Virus had to rear it's ugly head over here.

Mosquito fish (gambusia) have been introduced widely around the country. In some cases there hasn't been much effect on local native fishes and in other cases, the results have been pretty devastating. They really don't control mosquito larva any better than other small fish, but tend to out-compete many native fish for some reason (the live births probably help in this regard).

I read that an adult female Gambusia can eat a couple hundred mosquito larvae a day...sounds pretty impressive to me, but I don't know what the numbers are for other mosquito larvae-eating fish. And depending on what site I go to I get different info on their impact on the environment...all I know is that I have a 5 gallon tank of these little guys on my kitchen counter and they love freeze-dried blood worms, baby shrimp and tropical flakes!

Marisha - if I were you, I'd just enjoy them, which is what it sounds like you're doing.

Marisha, what knd of filter do you have in that 5 gallon tank? I ask because my daughter wants to set up a 2 1/2 gallon in her room and I don't know what to filter it with.

-andy

I have a UG filter with a power head that was originally for a rectangular 10 gal. It is made up of two black grated plates that can connect and each has a powerhead...I am using only one of the plates and powerheads and had to cut the plate with large wire cutters (even though it's plastic they worked like a dream) because my tank is dome fronted so I needed to round the front of the plate so it would fit...I also have A LOT of gravel in the tank so the plants sit really deep and they don't get disturbed much when I siphon the debris. Your daughter's tank, what shape is it?

Mosquitoe fish are horrible fin nippers, way worse than any of my FW puffers, they are a risk to native fish and its good that you caught them, your wildlife services should be using native minnows, as they are not invasive and also eat lots of mosquitoe larve.