Phytoplankton are basically the microscopic plant-like organisms, photosynthetic creatures that drift about in the ocean and absorb the sunlight turning it into delicious sugars. Looking at their essence in your saltwater tank, the filter feeding invertebrates such as the sponges, corals and clams will finally feed on the phytoplankton for their nutrition. Phytoplankton have been billed a good source of nutrition for your marine life looking at the fact that they have a generally high level of concentration in Omega 3 unsaturated fatty acids which happens to be one of the key nutritional needs in a number of the invertebrates.
Talking of the phytoplankton strains that you can grow at home for your saltwater tanks, there are three basic and most common kinds. These are the Nannochloropsis, Isochrysis, and Tetraselmis. And in all of these strains of the phytoplankton strains that you can culture in the home for the saltwater aquariums, one that is seen to be the most popular is the Nannochloropsis. This is the particular phytoplankton strain that is largely seen to be the best for the fact that it happens to be well balanced, having such better levels of concentration of the essential fatty acids, HUFAs and EPA, which are more than essential for the growth of the fishes at their larval stage of development. As such if at all you have plans for breeding saltwater fishes in your saltwater aquarium, then the best strain of the phytoplankton to go for is the Nannochloropsis. Over and above this, Nannochloropsis has as well been deemed to be a good fit for saltwater aquariums for the fact that it has some antibacterial properties.
You can choose to culture or not to culture your own phytoplankton anyway. The reality however is that growing your own phytoplankton will be a bit of an investment in time and energy as it takes some time for you to set up your culture station and to have them grow. Moreover, even though the phytoplankton strains mentioned above have the hardiness to continue the growth on their own after then, you will need to ensure that you have spared some time on a daily basis for you to maintain the culture set up or else you run the risk of seeing the culture crash. To escape all these kinds of inconveniences with the growth of your phytoplankton on your own, you can make use of the available commercial products and use them to dose your saltwater aquariums with the phytoplankton strain of your choice.
Note the fact that many aquarists do dose phytoplankton into their aquariums as a supplement to the feeding schedule given the fact that they happen to be so natural and nutritious food sources for marine life.