It may be contaminated, or will at the very least, throw off the temperature and P.H. Allow the fish about two hours to become acclimated before feeding. Only feed an amount that can be consumed in the first two to five minutes. Overfeeding is a common problem in an aquarium. It is important not to overfeed, because excess food will become debris adding to the ammonia levels. Once you have removed all the gravel, transfer it into a strainer of some sort and run it under hot water. Be sure to mix it up while you are rinsing so that all the sediment and waste is removed. Once the gravel has been cleaned, place it aside. You will not be putting it back in the tank at this time. You may have to adjust the feeding times depending on what your schedule is now and what other types of fish inhabit the tank. With the number of species of Armored catfish, you will be sure to have a colorful and amusing aquarium with the addition of these comical fish. As with all fish, be sure to keep the aquarium clean and healthy so as to ensure the health of the fish as well as your enjoyment for years to come. After the purchase of your tank, you can now consider how you wish to decorate it. Many types of gravel and sand are available in a lot of colors. You can add accent plants as well to make it appear more natural. Many people add little figures or signs to personalize their aquariums. It's all up to you in regards to d cor. So after about a month, if all is well with the tank and the fish seem to be adjusting well, then it is okay to introduce some new marine life. A mandarin fish or a dwarf angel fish might round out the collection nicely, and they are fairly compatible clown fish. Whenever adding new fish, choose the species carefully for compatibility. They can't be kept together for obvious reasons. The water temperatures vary greatly. Tropical fish are usually brighter in color, and therefore more appealing to aquarium lovers than the fish available in the cold water variety. Most people are somewhat familiar with a few tropical fish such as the Clownfish or the Angel fish.