i have 2 Plecos (Hypostomus plecostomus), in my tank, those that feed on the algae and stuffs from the tank? Well, 2 nights ago i noticed it's eye blinked, which gave me a shock, i never knew fish had eyelids, then last night i looked at it again, and again it blinked at me. Weird thing was, it only blinked once. And that i'm very sure. Can these fish blink?