Ancistrus dolichopterus

Ancistrus dolichopterus
Starlight Bristlenose Pleco (L183)
This species has now been correctly identified in the hobby. For many years this species name was used for the common bristlenose (now known simply as Ancistrus species 3) and other similar species. Images and information describing it it in much of the available literature confirm this confusion. 

It's a very beautiful fish, but it can be difficult to keep alive, especially if kept in hard, alkaline water and, as such, is not really a good beginners fish. It can also be difficult to identify correctly and is often confused with similar looking fish, such as A. hoplogenys. So similar are some of these species that a definite id is sometimes impossible without knowing the collection locality of the fish. 
The overall appearance of this species is not as useful for identification as you may think - there are many Ancistrus species which have a dark base with small white dots as colour pattern. There is however a key that differentiates this species from all other (currently known) Ancistrus species - it's the only species with one hard and nine soft dorsal rays (I,9). Also encountered under the name Ancistrus hoplogenys.