Perhaps you're thinking of one of these:
* Algerian fish: This could refer to any fish species found in the waters surrounding Algeria, but it's not a specific type of fish.
* Algae eater: This refers to a variety of fish species that are known to consume algae in their environment. Some popular examples include Siamese algae eaters, plecos, and otocinclus.
* Another fish species: Could you provide more context? Perhaps you heard a name slightly different than "alger fish"?
Please clarify what you mean by "alger fish" and I'll be happy to help you further!