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Get a tank. Gather harvesting equipment. Purchase minerals to encourage algal growth. Buy a spirulina culture.
Most home growers find that a standard size aquarium is perfectly adequate as a space to grow spirulina in. A tank that size will supply a family of four with plenty of spirulina. You can grow spirulina in larger tanks, or even in a basin or pool outdoors (if you live in a warm climate). However, it will be easier to manage the spirulina culture indoors in a small tank. A spirulina colony can appear thick, but it's mostly water. Once it's ready to eat or use, you'll want to squeeze out the excess water. For most home growers who will want to use only a small amount of fresh spirulina at a time, a fine cloth or mesh will work just fine. In addition, you'll need a scoop to get the spirulina out of the tank. If you want to harvest larger amounts of spirulina to dry, get a larger supply of fine cloth or mesh to make things easier. Trying to grow spirulina in plain water won't necessarily lead to great results. To have an optimal colony, you'll need to add specific minerals. You don't have to be an expert, though--you can buy premixed mineral "food" for spirulina from health and organic stores as well as online. Make sure that it contains: Sodium bicarbonate Magnesium sulfate Potassium nitrate Citric acid Salt Urea Calcium chloride Iron sulfate Ammonium sulfate To get your own spirulina colony going, you'll need a bit of live spirulina as a starter. Check with your local or favorite online health food or organic supplies store and ask for a spirulina starter kit. Spirulina starter cultures are usually as simple as a bottle containing spirulina algae in its medium (water). Buy spirulina cultures only from sources you trust. Since spirulina can absorb heavy metals and other toxins, you want to ensure that the starter supply has come from a safe source.