In one sentence, describe what the following article is about:

Rainbow sharks are omnivorous and can and should eat most anything. Sharks will eat any common fish food, including pellets, flakes and algae wafers, as long as it sinks to the bottom of the tank. To give you sharks a brighter coloration, make sure to feed it small crustaceans a few times a week. Feed your shark two to three times daily.  Experiment to determine how much you should feed your fish. A fish should eat its food within approximately five minutes. If anything is remaining after that period of time, you have given your fish too much food. Excess food will ultimately make the tank dirty.  Good crustaceans or insects to feed your fish include brine shrimp, bloodworms, Daphnias, and artemias.  You should also feed your sharks vegetables. Try Zucchini that has been sliced into small bits and boiled. Boiled peas can also be good. Rainbow sharks will eat some raw vegetables, including romaine lettuce, beet tops, and swiss chard. When feeding your fish cooked vegetables, be sure to let them cool before placing them in the aquarium. Clean the tank weekly. When you clean the tank, you do not need to remove all of the substrate (sand or gravel), however, you should use a siphon to suck up the waste that accumulates on the bottom of the tank. Use a scraper to remove algae from the glass. After finishing these tasks, remove and replace 10-15% of the water.  Do not remove fish when changing the water. This will cause unnecessary stress. When replacing the water, put new water into a bucket. Do not use this bucket for any other household tasks (it might accumulate dangerous chemicals). Test and treat the water as discussed previously. Use a siphon to slowly introduce the new water back into the tank. . It is particularly important to watch for signs of illness with fish. That because many fish diseases are highly communicable and will spread rapidly throughout the tank. Many common causes of illness are also the result of bad water conditions and might quickly kill off all of your fish. Things to watch for include:  Scratching against objects in the tank Duller coloration, changes in color pattern, and spotting Gills and fins that have been chewed on Lack of energy Fins tightly held against the body Bloating Gasping for air at the surface of the water Disappearing fin or tail
Feed it a diverse diet. .  Watch for signs of illness