In order for the green algae to bloom and establish its presence in the marine saltwater tank, there are basically few requirements that must be met. Warm water is of course one of it but the main requisite is that there must be adequate lighting that comes from either natural sunlight or artificial metal halide. Apart from that, nutrient is also another source or factor that promotes their growth and it must also be abundant. High level of nutrients usually is a result of overstocking of the marine systems and during the time when the corals, live rocks and other aquatic plants have not yet established their population, the green algae will take advantage of these conditions to grow very fast. Due to their nature of easy and rapid reproduction capability, you might find green marine algae establish their foothold quickly and extensively and will overrun the system in a matter of days.
Sometimes despite your best effort to avoid development of green algae, it will not always be successful. You will find that at one time or another, these problems often get out of hand especially if you have a mini fish tank as your marine setup. While totally eliminating them is highly impossible, your biggest challenge is how to control their growth and population. First of all, changing the lighting system to those that comes with a timer that controls the lighting period should provide a good start. This will ensure that your tank gets sufficient light for the aquarium inhabitants to grow while prevents overrun of the system with green algae growth. Aquarium skimmer will also offer another value added advantage apart from just being a typical fish tank filter. A high quality and well-maintained skimmer will help to get rid of most of the nutrients present in the water and overall, this will reduce the chances or likelihood for algae bloom to develop.
Another way to deal with the algae problem is to use algae-eating marine fish and invertebrates. Turbo snails, krill, shrimps, hermit and fiddler crabs which are all invertebrates while offer a feasible solution but however, it might not be advisable to have them around as they can actually harm your fish or ended up getting eaten. A sensible approach would then be using algae eating marine fish such as yellow tang, sailfin tang and the dwarf angelfish. These species while look nice and adds variety to the tank setup, also help to control the algae population. One common mistake made by aquarist is that with the presence of the fish, they are hoping that the algae will just disappear but in fact this is not entirely true as depending on their mood, sometimes they will just refuse to eat the algae. In the end, the best approach which works all the time even for brown or blue-green algae including also the deadly red slime algae problems is to reduce and control the nutrient levels in your fish tank.
Related: Algae control in freshwater aquariums