So my family and I were taking a walk down the San Antonio River, and we stopped to look at some ducks and ducklings on a bank. As one swam into the water I noticed several very large common plecos eating a dense layer of algae. I counted, and there were at least 5, almost certainly more. However, plecos aren’t native here. In the past, many fishkeepers in the southern US released their plecos into streams when they got too big for their tanks. In many places these plecos have established breeding populations, and are a serious pest. They are eating machines and outcompete many other local fish for food, have few predators, and because they’re not that edible there isn’t much reason for people to fish for them, so they’ve basically got free reign over the rivers they’ve been introduced to. Additionally their burrowing habits are thought to cause significant erosion in Florida, but I’m not sure if that’s actually a thing. So just keep in mind, if your fish is too big for your tank and you cant give it away, don’t release it, because it could completely wreck the ecosystem for years to come. A photo of said plecos: If you look closely you can see they’ve completely removed a thick layer of algae from the concrete bottom.