You have absolutely no idea what you're talking about, do you?
Also, this is a moot point. Even if there were things down there feeding off the bacteria - which there aren't; I've never heard of any worms living at the bottom of the sea, certainly no crabs, and CERTAINLY neither of them hanging around vents - that wouldn't erase the fact that the bacteria themselves don't eat or need light.
You need to get out more maybe?
Direct from the Wiki page on hydrothermal vents:
The ecosystem so formed is reliant upon the continued existence of the hydrothermal vent field as the primary source of energy, which differs from most surface life on Earth, which is based on
solar energy. However, although it is often said that these communities exist independently of the sun, some of the organisms are actually dependent upon oxygen produced by photosynthetic organisms, while others are
anaerobic.
The chemosynthetic bacteria grow into a thick mat which attracts other organisms, such as
amphipods and
copepods, which graze upon the bacteria directly. Larger organisms, such as
snails,
shrimp,
crabs,
tube worms,
fish, and
octopi, form a
food chain of predator and prey relationships above the primary consumers. The main families of organisms found around seafloor vents are
annelids,
pogonophorans,
gastropods, and
crustaceans, with large
bivalves, vestimentiferan worms, and "eyeless" shrimp making up the bulk of nonmicrobial organisms.
Tube worms, which may grow to over two meters tall, form an important part of the community around a hydrothermal vent. They have no mouth or digestive tract, and like parasitic worms, absorb nutrients produced by the bacteria in their tissues. About 285 billion bacteria are found per ounce of tubeworm tissue. Tubeworms have red plumes which contain
hemoglobin.
Hemoglobin combines with hydrogen sulfide and transfers it to the bacteria living inside the worm. In return, the bacteria nourish the worm with carbon compounds. The two species that inhabit a hydrothermal vent are
Tevnia jerichonana, and
Riftia pachyptila.
One discovered community, dubbed "
Eel City", consists predominantly of
eels. Though eels are not uncommon, invertebrates typically dominate hydrothermal vents. Eel City is located near
Nafanua volcanic cone,
American Samoa.
[10]
Other examples of the unique
fauna which inhabit this ecosystem are the
scaly-foot gastropod Crysomallon squamiferum, a species of snail with a foot reinforced by scales made of iron and organic materials, and the
Pompeii worm Alvinella pompejana, which is capable of withstanding temperatures up to 80 °C (176 °F).