A quick dumb question...

wow! u should really get only one pleco per tank. they get huge, are slightly aggresive and eat allllll the algae.
 
as was already mentioned, there are several different kinds of plecos and not all of them get big, not all of them eat algae, and not all of them are agressive.

also, define "tank". 10g tank? 55g tank? 125g tank?
 
With all fish, it's got a lot to do with individual personality. I have three large commons in the same tank. They all get along, they all stay in the same part of the tank. There's a little bumping and pushing at feeding time, but everyone eats well. The third common was introduced when he was only 2 inches, and the other two were well over 15 inches. No problems with them beating him up, but I've got very placid plecos. Introducing a rhino later was again, no problem. I've got a picture somewhere in my computer of a 1.5 inch rhino sharing a zuchini wege with a 19 inch common plec. Very cute. All depends on if they have lots of room, enough food often enough, and the individual personality of the fish.


Having said that, some species are more naturally social, and some more natually anti social. Royal Panaques often take a nasty turn at their own kind (breeding competition) but not to other species of plec. I've also seen tanks with 8 adult royals together, and no in fighting. When you get your bigger tank, you'll just have to see if the others will tolerate the company. I know I would'nt want to see my three commons seperated.
 
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