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. Generally speaking, phytoplankton has been deemed a sure source of good nutrition for marine life for the fact that they happen to contain such high concentration of the Omega-3 unsaturated fatty acids which are a dietary requirement for the majority if not all of the invertebrate marine life.
There are basically three kinds of aquarium phytoplankton strains that you can grow at home looking at your saltwater aquarium needs. These are the Nannochloropsis, Isochrysis, and Tetraselmis. And by and large, looking at all the available strains and kinds of phytoplankton that you can grown in your home for your saltwater aquarium, the one that actually stands out is 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. For this reason if at all you are considering the breeding of saltwater fishes in your aquarium, then this is the best strain that you will be advised to start with. Further to this is the fact that Nannochloropsis has as well been seen to have some antibacterial properties in it.
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. Over and above this is the fact that after you will have so set up the culture station, in as much as the strains mentioned above are as hardy and will go, you will need to spare some time for maintenance and monitoring of the set up on a daily basis or else the culture may crash. Instead of going through all the stress there comes with culturing your own strains of phytoplankton for your need to dose your saltwater aquarium, you can alternatively settle for the many available commercial products for the same purpose and avoid all the inconveniences there may be with the option of culturing your own.
It should be noted the fact that a number of informed aquarists actually are in the habit of dosing their aquariums with phytoplankton as a food supplement as they happen to be natural and as well highly nutritious food sources for marine life.