I have two rubberlip plecos, I've had them about 8 months. They do great, but I have a question, and finally remembered to post it LOL. I may just have a genetic mutatnt, but one is a solid grey, and the other has 5 or 6 yellow (more non-pigmented looking than yellow) spots on each side of the dorsal fin. Is this normal? If so, does it denote something? Is the other one the abnormal fish? LOL
Thought I'd get ya'lls thoughts!

I did a little rtesearch and the only available info pertaining to sexing rubberlips (bulldog plecos) is this:

Males have a somewhat larger head, slimmer ventral sides and disproportionately large pelvic fins. The oversized pelvics are most likely to keep sperm from floating away in the current prematurely during fertilization.

Other than that, there has been no mention of coloration denoting differences in phenotypes. It seems to be all in their heads and pectorals.

Does one of your plecos heads and pectoral look different than the other?

huh. I'll have to try and get pics at some point. I'll go look at them in about an hour or two- they usually start coming out around six, when the fish settle down

Sorry about that. I had a brainfart and thought you were wondering if one was male and the other female. It's been a while since I had "phenotype" as a vocabulary word in school!

Umm, well, there are several different types of rubberlips. Heres a few links to the different varieties:

These are true rubberlips:

rubberlip grey

rubberlip grey

rubberlip brown

And heres a link to a page that shows many different Chaetostomas (rubberlip family):

chaetostomas family

If the first set of pics doesnt look like yours, check the last one.

Hope this helps a bit! I'm looking forward to your pics.

Paul