My mum was sold a "cleaner fish" for my sons tank, she explained to the assistant it was for a small tank with guppies in and what was best, Mum being in her 70's and never kept fish before took the assistants advice and purchased a lovely gold plec. This was our first plec and I was horrified when I researched it and found it was a common and would grow far too big for a 30" tank. I phoned the shop but they wouldnt take it back. The more I looked into the common plec, the more I fell in love with them and my pride and joy are my common and gibby. But yet I dont think these beautiful inteligent creatures should be so cheap and readily available, but business is business and most LFS dont give a hoot about the fish so long as their tills keep ringing.
And therein lies the biggest misconception. Many folks believe they need a "cleaner fish" for algae or bottom duties when in fact, they are adding to the total amout of waste due to large amount of waste created by the larger species of plecos.
Many of these fish are actually quite poor at eating algae once they discover that fish food is much easier to come by. Others require special diets for some are herbivores ,some are carnivores,and some are omnivores. not all plecos will get along if housed together in anything but larger tanks and indeed,,,some will kill other plecos.
Have kept or am keeping many species from bulldog pleco ,snowball pleco,rubber lipped pleco, clown plecos,chocolate pleco,gold nugget pleco,royal pleco,whiptail (farlowella), candy stripe,bristlenose,and common pleco to name but a few.
Nearly all have different characteristics which must be realized BEFORE purchasing from my perspective.
Sadly, even with the info at your fingertips,, few seldom bother.