I'm interested in many different types of pets, including freshwater fish, and I enjoy sharing what I've learned about them.
One of the most popular and distinctive families of freshwater fish kept as pets is the plecostomus family. Usually, they are referred to as "plecos"—partly because it's a great nickname and also because of an old superstition. It was once thought that if you spoke or spelled out the entire name of "plecostomus," a pleco somewhere would die. So my apologies in advance.
Just How Large Can They Grow?
The majority seem to grow to 18 inches, but only after several years. This writer has seen plecos almost two feet long. However, most plecos never get that big. If you have a large tank or pond, don't completely dismiss the idea of getting a pleco. They are long-lived fish that are relatively easy to care for and have a unique beauty. The chances for a pleco outgrowing your tank are small.
Advantages of Plecos
Plecos are hardy, distinctive, and social (as in, they completely ignore other fish—unless it's another pleco). They are also bottom feeders, which is very helpful for keeping your tank healthy. They sift through the gravel or whatever you use on your tank's floor and eat the food the top feeders may have missed. If that food was left alone, bacteria could grow that could affect the health of the water.
They also eat any growing algae. Since you are sure to keep your tank healthy, you will most likely have to buy algae wafers for them to eat. Their food is also easy to find.
And they look so cool. They come in several colors and patterns, including a very striking black and white zebra. The brown types are the least expensive and easiest to find.
Disadvantages of Plecos
Plecos can often be aggressive to other plecos. They also will suck on any sick fish in the tank and can pester a sick fish to death. They are also notoriously difficult for the hobbyist to breed, but you might not want to, anyway.
The main disadvantage of a pleco is that they grow unpredictably; every pleco seems to grow in their own good time. Some seem to be content to stay under a foot all of their lives. And still others need to move to ever larger tanks and then a pond. Ask 10 pleco owners about how big and fast their plecos grow, and you'll probably get 100 different stories.
Plecos are not recommended for tanks under 10 gallons. They are sure to outgrow a 10-gallon tank eventually, although it will most likely take years. If you only want to keep a 10-gallon tank or less, consider a Chinese algae eater instead.
What Should I Do If My Pleco Gets Too Big?
If your pleco does turn into a record-setter, please do your best to find him or her a new home. The nice thing about plecos is that they are not to fussy about where they live. Call a pet shop or advertise on Petfinder.com or craigslist. If you know someone who has a backyard pond or koi pond, ask them if they need a bottom feeder to help keep the pond clean. If there is a public park or college with a man-made pond, ask them if the pleco can live there. Don't just dump the pleco in, unless you want to make a lot of enemies fast.
For a last thought, let me tell you about my Dad's pleco. He's about ten years old and still hasn't grown beyond six inches. The tank has just him and one other fish (a glassfish), and he seems to be doing great. So, although the possibility exists that he might outgrow the tank, the odds are he won't.