It most definately can be called a hybrid as it fits any dictionary definition of a hybrid. Example Oxford dictionary: "1. an animal or plant that is the offspring of two different species OR varieties."
A distinction can be made between a hybrid of species and a hybrid of strains, though in the aquarium hobby most people (though not all) use the term hybrid only to refer to crosses of different species. But actually, outside of the aquarium hobby, the word is used far more often to refer to crosses of different strains. Example: in agriculture the offspring of 2 different breeds, strains or cultivars are most certainly called a hybrid. Same thing in dog breeding, when 2 different breeds are crossed, the offspring is called a hybrid. And rightly so, as it fits any dictionary definition of the word!
