Mosquitofish nearly any small fish can be used,

                  Mosquitofish Dye Experiment    I am interested in this because no one has tried using bait dye on anything except fishing bait, while it could be used for other purposes. Also, mosquitofish are very small, and different ratios of dye could kill them but not harm larger minnows. In many parts of the world, mosquitofish are a damaging invasive species. If the mosquitofish are treated with dyes to make them more visible to predators or to poison them, it might help lower their numbers in other parts of the world.    The dye I will be using for this experiment, Pautzke Fire Dye made by Pautzke Bait co., is the only known commercial live bait dye. It is specially made for dyeing live bait, and is very effective. There are several colors of fire dye, including blue, pink, green, red, and gold. This bait dye works on both saltwater and freshwater fish. The idea of changing the color of living fish is new, and is becoming popular worldwide. http://www.pautzke.com/learn-to-catch-fish-with-live-fire-dye-minnows/ http://www.pautzke.com/test-complete-fire-dye-works-on-saltwater-baits/    Fishing has been around for thousands of years, and many methods have been invented to entice a fish to bite the hook. The first record of artificial lures was in the early 17th century, and they were probably used before that. Live bait became popular for pike fishing several centuries after, but it was only recently that live bait has become popular worldwide, in  both freshwater and saltwater. A few years ago, the idea of dyeing live baits started, and is starting to grow in popularity. This dyeing concept could be used for more than bait. http://www.fishingmuseum.org.uk/baits_overview.html    Most of the freshwater game fish caught in north america are caught on live bait, and nearly any small fish can be used, alive or dead. Shiners, killifish, mudminnows, sculpins, and shad all make excellent live bait in freshwater. Mosquitofish and other livebearers however, are not commonly used because of their extremely small size. Despite this, many small to medium sized gamefish will readily devour mosquitofish just as much as worms or conventional baitfish. Dyed mosquitofish would present a tasty, brightly colored meal to any predator fish, and could increase the chance of catching fish. (Sternberg, pg. 18 – 25)   Mosquitofish are native to the southeast United States, and can survive in almost any puddle, pond, or swamp in freshwater or saltwater. They grow to 1 ½ inches long, and are olive green, grey and brown. They tend to live in the shallowest water with plenty of water plants or caves to hide in. They primarily live and swim at the surface of the water, making comparatively easy for predators to attack from below. They are very hardy, and can live in freshwater, saltwater, or brackish water. This makes them the perfect fish for beginner aquariums, and they can easily learn to eat fish food flakes. This means that in a foreign ecosystem, they can multiply quickly and wreak havoc. https://www.sms.si.edu/irlspec/Gambusia_affinis.htm    The ability to breed very quickly allows them to survive in their native home, but can allow them to destroy a new habitat. Mosquitofish are ovoviviparous, which means that the eggs hatch inside the female, and the babies are born fully developed. A female can give birth to up to 70 babies at a time. They feed almost exclusively on insect larvae and small crustaceans, but will gladly devour the eggs and babies of other fish. They will also bully out other minnows in an area. Mosquitofish don’t need much to thrive. They can live in any temporary body of water, fresh or salt, and only need a few square inches of surface cover to hide in. https://www.sms.si.edu/irlspec/Gambusia_affinis.htm    In Australia, mosquitofish are one of the worst invasive species. They can survive in poorly oxygenated, shallow waters that other fish can’t, they are quite aggressive for their size and can push out other fish, and they eat all the food in an area. They were introduced in the 1920s for mosquito control, but proved to be less effective than native species. Now, there are so many of them, and they are so damaging to the ecosystem, that many australians call them “plague fish”. Many solutions have been tried to eradicate them, but all of them have failed. If there was a certain poison for them, or a way to make them more attractive to predators, it could help lower their numbers. https://www.dpi.nsw.gov.au/fishing/pests-diseases/freshwater-pests/species/gambusia    The science of dyeing live fish is still new and expanding. It works very well for bait, but it could also work for population counts, ecosystem health measurements,  and invasive species control. The fire dye from Pautzke Bait co. works well for temporary fishing bait, but it wears off in un-dyed water. More permanent dyes are needed for long term effects. No one has tried dyeing mosquitofish as of yet, but it should work on them like it does to other fish. Bait dyes could be used in several areas of science, and could help to expand our knowledge about chemicals and aquatic creatures.     Mosquitofish, despite their availability and hardiness in captivity, are only recently being used in the laboratory. The most recent studies are about sexual dimorphism, which means that male and female mosquitofish look different. However, they have not been totally ignored, scientists have been arguing over the number of species and subspecies of mosquitofish for decades. Currently there are 2 common species in the U.S., the eastern mosquitofish and western mosquitofish. The Western mosquitofish is the one that is causing problems around the world. There are many useful experiments that could be done with mosquitofish concerning the health of an ecosystem, the water table, and predator fish’s diets. https://news.ucsc.edu/2015/10/mosquitofish.html    The mosquitofish is only one in a huge group of small minnows known as livebearers, because of their ability to give birth to live young. You have probably seen several of them in pet stores, the most famous of which is the guppy. Guppies (poecilia reticulata) are a hardy, easy to keep aquarium fish sold across the world. Many color variations of the guppy have been bred to look more attractive and rare. Other species in the genus “poecilia” are also found in pet stores. The Endler’s guppy and Sailfin molly are two of them. The mosquitofish itself is in the genus “Gambusia” which contains over 20 species. In the lab, the common guppy is the most commonly used fish. It has been used in water clarity tests and many genetics experiments. The Bahama mosquitofish is being used more recently, and tests have shown that the bright colors on the dorsal fin of this species can change from population to population because of the amount of predators and the water clarity. https://appliedecology.cals.ncsu.edu/absci/2017/02/mosquitofish-risky-business/http://animal-world.com/encyclo/fresh/livebearers/livebearers.htm    With all of this information, it is clear that mosquitofish and other livebearers are relatively new in the modern laboratory. There are still many things that we can learn from them and about them. New products like Pautzke fire dye are just the beginning of a new breed of vibrantly colored fish, and more permanent dyes are already being developed. This experiment and others like it is going to test the waters of a combination of fish dyeing and the increasing research on livebearers. Brightly colored mosquitofish can be used in all sorts of practical applications, such as water flow, population movement, predator diets, and it could help to solve invasive species problems.