Fish tanks as vectors for accidental introduction of exotic species
Invasive, Invertebrates 
Planted freshwater aquarium.Freshwater home aquariums pose a risk for accidental introduction of exotic invertebrates to natural areas according to new research in the journal Biological Invasions.
As the owner of a freshwater fish tank, I was particularly intrigued by this study when I came across it.
For many aquarium hobbyists like myself, owning a tank is not just about having colorful fish swim around but also about creating a mini-freshwater ecosystem with plants and natural features like driftwood and rocks.
One of the pleasant surprises of a freshwater aquarium are the invertebrate organisms like snails and worms that show up (probably hitching a ride with plants) and call your tank home.
However, as Ian Duggan from the University of Waikato found in his study in New Zealand, some of these incidental aquarium dwellers are actually exotic species that could pose a problem for natural freshwater systems if they were ever accidentally released to the wild.
Duggan hypothesizes that this could potentially occur depending on how aquarium owners disposed of their water after tank cleanings.
In his study, he sampled 55 freshwater fish tanks from 43 households and recorded 55 incidental invertebrate species including copepods, ostracods, cladocerans, molluscs, mites, flatworms and nematodes.
Of these, 6 were known established exotic species in New Zealand while eight others were not previously recorded in the country.
To help improve best management practices, Duggan also conducted surveys of the fish tank owners. He found that a small minority engaged in high risk behaviors by disposing of fish tank water in ponds or down storm drains.
Most disposed of their tank water by discarding it directly in gardens or by pouring it down the sink. Pouring tank water down the sink is generally low risk in many areas where the water enters the sewer system and is treated.
Nevertheless, Duggan recommends that aquarium owners dispose of their water by pouring it on gardens because the risk of accidental introduction of exotic species is nearly zero using this method.
--by Rob Goldstein
Duggan, I. (2010). The freshwater aquarium trade as a vector for incidental invertebrate fauna Biological Invasions DOI: 10.1007/s10530-010-9768-x
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