In terms of your corals and coralline hair algea can out compete the coralline for space to grow and can harm corals by irritating the base.
Most people do not like the look of the hair algae and its ability to grow fast and smother your LR, corals, or coralline therefore it is generally called a nuisance algae.
The benefit of the algae is that it does consume nitrates and phosphates helping to maintain cleaner water conditions.
This is why some people keep a refugium or algae scrubber. The algae can be grown for the benefits without being in the main tank causing the problems mentioned above. Caulerpa algae is mostly used in the refugium/algae scrubber.
Here are some ways from a post I wrote awhile back to help control algae in the main tank.
Avoid using untreated (not filtered) tap water if possible. Some sources are better then others but almost all untreated tap water will contain impurities.
Untreated tap water is a major source of algae problems. The tap water may contain phosphates, nitrates, silicates, heavy metals, as well as other impurities many of which are not good for the aquarium.
For top off and water changes use a high quality water source like reverse osmosis (RO) and/or distilled (DI) water.
RO and/or DI units are available for the home. High quality water may also be purchased from a store, vending machine, or a local fish store (LFS).
A protein skimmer can go a long way in helping to control an algae problem.
A protein skimmer will reduce the levels of DOC in the aquarium, help with lowering CO2 levels, and indirectly reduce nitrates by removing the DOC that would eventually be decomposed into nitrate.
A skimmer can also be a source of algae if not maintained properly. Just like any other filter media a skimmer should be cleaned on a regular basis.
Don’t over feed. Over feeding helps feed the unwanted algae in your tank
Food that settles on the bottom starts to decay given the algae a free meal. As much as 90% of the food given to fish can end up as nitrates so you can see where over feeding can be a big problem.
Many foods contain unwanted additives such as phosphates as well.
Make sure your lighting is of the proper spectrum. A low K value will help promote algae growth.
Cutting back on your lighting period may help control any nuisance algae as well.
Perform regular water changes using only high quality water.
A water change will immediately reduce the amount of nutrients in the aquarium. If there is a lot of detritus in the tank stir this up and siphon it out during the water change.
A crushed coral (CC) substrate will often trap detritus and there for it is a good idea to use a gravel vacuum on the CC during a water change.
The frequency of water changes depends on the level of nutrients and/or the bio load of the tank.
Also make sure to use a high quality salt mix when performing water changes.
Make sure your clean up crew is doing the job. If you don’t have a clean up crew think seriously about adding one to your system.
Some common critters in a clean up crew include snails, small hermit crabs, other crabs like sally lightfoots or emerald crabs, brittle and serpent stars, some types of shrimps, and sea cucumbers.
The above-mentioned animals as well as others will help control algae by eating it or cleaning up the uneaten food from the rocks and substrate before it begins to decay.
Introduce fish to your system that will eat algae.
Some fish will gladly consume certain types of algae as part of their regular diet. Here is a brief list of some of those fishes.
Yellow Tang, Sailfin Tang, Kole Tang, lawnmower blenny, bicolor blenny, as well as many other fish including some angels and rabbit fish.
Physically removing the algae is an obvious but not always thought of way to control nuisance algae.
Dieing diatoms can add silicates to the water thus contributing to the new growth of the algae. Also dieing green algae can add nutrients to the water to promote new growth of nuisance algae.
Physical removal of the algae may also help your clean up crew from being over whelmed.
As you can see the physical removal of algae can have both immediate and long-term effects.
Introduce macro algae to the system.
Macro algae such as Caulerpa grow fast and can out compete nuisance algae for the available nutrients in a system.
Caulerpa will need to be trimmed down from time to time also but is much easier to control then nuisance algae.
Patience and persistence are required from the aquarist to rid their system of a nuisance algae outbreak. The scourge of the marine aquarium can be controlled if basic guidelines and good aquarium maintenance practices are followed.
