Aquarium pets are showing up in some unlikely places, and that’s bad news for native species 
 
 
 
 
 
 Gigantic goldfish, like this one held by University of Nevada-Reno researcher Christine Ngai, have been found in the waters of Lake Tahoe. Image: Heather Segale 
 
 A new kind of lake monster has been found, in the depths of Lake Tahoe: gigantic goldfish. Researchers trawling the lake for invasive fish species scooped up a goldfish that was nearly 1.5 feet long and 4.2 pounds. 
 
 "During these surveys, we've found a nice corner where there's about 15 other goldfish," environmental scientist Sudeep Chandra of the University of Nevada, Reno, told LiveScience. "It's an indication that they were schooling and spawning." The arrival of the fish, which were probably dumped there by aquarium owners, has Chandra worried — goldfish are an invasive species that could interfere with Lake Tahoe's ecosystem. 
 
 It's unclear whether the giant fish were introduced as fully grown adults, or while they were still small, Chandra said. But even a small creature can have a big impact, if there are enough of them. 
 
 The goldfish are just one of several species of invasive warm-water fishes in Lake Tahoe. "The invasion is resulting in the consumption of native species," Chandra said. What's more, the invasive fish excrete nutrients that cause algal blooms, which threaten to muddy Tahoe's clear waters. [Photos: Giant Goldfish & Other Freaky Fish] 
 
 Fish out of water 
 
 Aquarium dumping has become a common practice in the United States and elsewhere, and it's taking a toll on native wildlife. A recent reporton California's aquarium trade found that fish owners and importers are introducing hardy, nonnative aquatic species to California waters. "Globally, the aquarium trade has contributed a third of the world's worst aquatic and invasive species," Williams, who was lead author of the report, told OurAmazingPlanet, a sister site of LiveScience, in January. 
 
 While the exact number of aquarium owners dumping fish is unknown, scientists know the practice is occurring because these species could not have ended up in these waters naturally. Between 20 percent and 69 percent of fish keepers surveyed in Texas admitted to dumping, according to Williams. 
 
 Other ways that invasive species find their way into natural ecosystems include aquaculture, live seafood, live bait, and fishing and recreation vessels. More than 11 million nonnative marine organisms representing at least 102 species arrive at ports in San Francisco and Los Angeles alone, Williams has found. 
 
 The invaders include tropical fish, seaweed and snails. One of the nastiest is a deadly type of seaweed known as Caulerpa. A type of algae that produces toxic compounds that kill off fish, Caulerpa was eradicated in 2000 (at great expense) from lagoons in Southern California. 
 
 Aquarium owners should be more careful when disposing of unwanted fish and other animals, Williams cautioned. "It's pretty simple: Don't dump your fish," she said. Instead, she suggests calling the pet shop that sold the fish or your state department of fish and wildlife. (Euthanasia is another option, but simply flushing fish down the toilet can be problematic — for the fish and for your plumbing.) 
 
 So why do people dump fish? Studies of dumping have shown that size and aggressiveness of the fish are two main factors, Williams said. 
 
 The largest pet goldfish, according to the BBC, was a fish named Goldie that was 15 inches (38 cm) long and weighed more than 2 pounds (0.9 kg). 

 The highly invasive lionfish is easily available through aquarium and internet sales and represents a potential threat for California waters. 
 
 CREDIT: Christian Mehlfuehrer/UC Davis 
 
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 In the film "Finding Nemo," a plucky clownfish escapes an aquarium tank thanks to some sage advice: "All drains lead to the ocean." 
 
 But in real life, flushing Nemo wouldn't end happily. Aquarium species are some of the hardiest fish and plants in the world, and tank owners and importers who dump unwanted marine life are introducing tough, non-native species to California waters, says a new report on the state's aquarium trade. 
 
 "Globally, the aquarium trade has contributed a third of the world's worst aquatic and invasive species," said Sue Williams, lead author of the report and an evolution and ecology professor at the University of California, Davis Bodega Marine Laboratory. That includes both marine and freshwater species, she said. 
 
 In California, 13 species found only in dentist's offices or other fish tanks have escaped to the state's marine waters, presumably due to release by aquarium owners or importers. 
 
 "We have no data on how many aquarists dump their organisms into natural waters, we only know that they do so because these are species that could only come through the aquarium trade," Williams told OurAmazingPlanet. A survey of aquarists (people who keep fish) in Texas, cited in the UC Davis report, found 20 to 69 percent of them admitted dumping, she said. 
 
 The report is one of six that the UC Davis Bodega Marine Laboratory prepared for the state, each exploring a different vector, or pathway, through which invasive species can enter California ocean waters. The other pathways include aquaculture, live seafood, live bait, fishing vessels and recreation vessels. 
 
 Every year, San Francisco and Los Angeles ports see more than 11 million non-native, ornamental marine individuals — such as tropical fish, seaweed and snails — bound for aquariums, representing at least 102 species, Williams and her colleagues discovered. [Image Gallery: Freaky Fish] 
 
 One of the worst introduced species is a killer algae. Though actually a type of seaweed, the species Caulerpaearned its nickname when it infected two lagoons in Southern California in 2000, costing more than $6 million to eradicate. 
 
 Though most imported marine life comes from Indonesia and the Philippines, where ocean temperatures are warm, the report found 34 species could survive in California's chilly bays. "[Aquarium species] are highly likely to survive in the wild, because they have to be so tough to survive the trade," Williams said. Some can even survive a trip down the toilet, she said. 
 
 One potential invader is the lionfish, a venomous predator that gulps down smaller fish. In Florida and the Bahamas, authorities have organized fishing derbies to counter lionfish attacks on local reef fish. 
 
 Williams said a little outreach could prevent the lionfish and other predators from gaining a toehold in California. "[The aquarium trade] might be the vector that is most easily managed, because it really just requires public awareness." 
 
 Williams recommends aquarium owners who want to toss live fish call the pet shop that sold the fish, trade or sell fish on eBay (where it's legal to do so) or ask the California Department of Fish and Wildlife for advice. If all else fails, — or "if they're queasy about getting rid of it," William's euphemism for killing — she advises to remember it's for a greater good. 
 
 "When these species are released, they can do some major ecological and economic harm," she said. 
 
 Reach Becky Oskin at boskin@techmedianetwork.com. Follow her on Twitter @beckyoskin. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.
– Planning a vacay to Lake Tahoe? You may well encounter goldfish that are 1.5 feet long and weigh more than 4 pounds, Scientific American reports. Researchers trolling for invasive species encountered the massive goldfish and say pet owners may have dumped them. That act of good will, however, could damage the lake's ecosystem when the goldfish eat native species and excrete a nutrient that muddies the water by causing algal blooms. So-called fish dumping is nothing new: "Globally, the aquarium trade has contributed a third of the world's worst aquatic and invasive species," says the lead author of a report on California's aquarium trade. Owners often discard them because the fish are too big and aggressive, he adds. As for the monster goldfish, only 15 have been found so far, swimming "in a nice corner," says a scientist. "It's an indication that they were schooling and spawning."