Catching foot-long Plecs with my bare hands - now that's what I call a blast.
YEE - HAW!
Plecostomus do not have a slime coat, and their armour is far too strong for them to be injured by being caught and hauled out of the water. In fact, I can honestly say that catching Plecs by hand is not only the easiest way for us, it's the least stressful way for them (if done properly).
Now, I myself have only tried to do it by hand and with a net, but I hypothesis on the results of other methods below. I may be wrong; probably am, in fact.
Net; threads get caught in gills, on armour, and on spines = not good.
Plastic bag; may succeed in capture but the Plec will surely puncture it, leaving the Plec standed either out of water or in a vacuum = even worse.
Plastic container; probably the best of these three, but will be incredibly difficult to manouver because it is not hydrodynamic.
"
Jar trap"; very clever but presents a critical problem, because the Plec will not have access to air = deadly.
A Plec's face shield is strong enough to withstand, completely unharmed, a full-on charge into a wall of glass. To catch a Plec, you simpy corner it; their last defense will be to "lock up", at which point you drag them out of the water and into the transport container.
Do Not try to grab them while still swimming or uncornered; their caudal pundicle is tremedously powerful, and their thrashing motions may cause them stress, as they smash into rocks and walls, damaging their fins and possibly their eyes, or if out of the water, throwing their weight around excessively.
-Lynden