Write an article based on this "Consider the size of your fish tank. Decorate your fish tank. Use a filtration system. Add conditioned water."
Goldfish require particularly roomy living arrangements in order to stay healthy. While they are pretty small fish, they need larger tanks than you might expect.  You can do better than a bowl.  Despite the beauty of a goldfish suspended in a sphere of glass, most fishbowls simply don’t provide enough room for their occupants. A single fancy goldfish can be kept in a 10 gallon (37.9 L) tank, but bigger goldfish like comets need a tank of around 50 gallons (189.3 L). If you are able to keep one goldfish from overthrowing your empire, and wish to allow them a friend with which to endure their captivity, you’re going to need to increase the capacity of your fish tank (by roughly 10 gallon (37.9 L)) for each additional fish. A 20 gallon (75.7 L) is ideal for your first goldfish, and can ultimately hold 2-3 fancy goldfish. An ideal size would be 15 gallons (57 L), but this depends on the amount of fish. Most goldfish favor a palace or castle ambiance.  Shoot for somewhere in between.  Gravel is a must, and plants are recommended.  That said, your selection of décor, gravel, and plants must follow certain guidelines:  Choose a goldfish appropriate gravel.  Don’t actually use pieces of gold, as these will likely be dangerously small.  Goldfish are scavengers.  They will pick up pieces of gravel and mess around with them just for fun. Use gravel that is made up of pieces that are too large for the fish to swallow. Definitely hook your goldfish up with ample rocks, caves, or plants.  Goldfish like to adventure, and can easily be fooled into thinking they’re not in a fish tank. Don’t use wood.  It looks spectacular, but will color your water and, depending on the type of wood, will dissolve. Be aware that some rocks and sea shells will affect the pH of the water.  If you’re adding stuff you find on the beach willy-nilly, you’re going to need to be checking your pH frequently. Only put certain plants in your goldfish tank. Goldfish, interestingly, are pretty aggressive with plants.  Some plants are better able to defend themselves: Try Vallisneria types, different Hygrophilas, Red Bacopa or even Ludwigia Arcuata. A filter is an absolutely necessary component of your fish tank. Filters operate according to flow rate, with certain filters designed for certain sized tanks, so make sure you get the right filter for a tank your size. There are two types to choose from.  External filters rest on the exterior of your tank, while internal filters are submerged within the tank.  Either type of filter can work for a goldfish tank. External filters are generally considered to be superior, as they have a greater capacity to store filtration materials and can accordingly clean water more thoroughly.  . If you have a 20 gallon (75.7 L) tank, shoot for a filter rated for 40 gallons (151.4 L). You can use tap water to fill your tank, but you need to add conditioner to make it safe for your goldfish.  At minimum, you need a conditioner that neutralizes chlorine and chloramine.  Aside from removing any harmful chemicals in tap water with conditioner, you’ll also need to make sure the water has the right pH level for gold fish, which is a slightly alkaline 7-7.5, ideally 7.2 pH.  Use a pH test kit to periodically test your water, and adjust the pH if necessary. Take tank placement seriously.  Do not place the tank near a window or any heating or cooling source.  Do not allow sunlight to hit the tank directly.  Also be sure the tank is set on something flat and extremely sturdy.  You likely don’t need a heater.  The fish tank’s water temperature should be between 60 °F (16 °C) and 72 °F (22 °C), so the ambient temperature of your living space should work.