There are numerous sources and controls for problem algaes....below is a long but very useful article written by a famous person here that needs to re-posted once in a while just because it covers the subject so well....happy reading.
NMReef
Algae Issues
At one time or another most marine aquarists have experienced an algae problem.
Below are some of the most common types of nuisance algae and what can be done to control them.
I fell it is important to note however that some algae in an aquarium may not necessarily be a problem. In fact some fish and inverts consider many types of algae to be a source of food.
Algae becomes a problem when it starts to interfere with the aesthetic appeal of the aquarium or when it starts to over take the live rock (LR) or starts to irritate a coral.
Diatoms:
Usually appears as a brown dusting or film on the glass, LR, or substrate.
The brown dust that is seen is actually not the algae but dead diatom skeletons linked together. Many times this is the first algae to develop in an aquarium and is often seen within the first four months of setup.
Diatoms need silicates to grow and only last as long as there is a supply in the water. One of the most common ways silicates are introduced to the tank is through the use of tap water. Untreated tap water may contain silicates as well as other unwanted additives to the aquarium. Other means of silicate introduction can be the use of play sand that contains silicates or the curing of LR.
Hair Algae:
Usually appears as a green hair like or grassy growth on the LR.
This algae can also grow on the substrate, glass, powerheads or even slow moving animals like snails but are most common on LR.
This is one of the most hated algae in the marine aquarium because it will grow on almost anything and has the ability to spread fast and completely cover the LR in a tank or smoother and irritate corals.
Hair algae usually like an area in the tank with high light and a moderate to high current flow.
Red Slime Algae / Cyanobacteria:
Usually appears as a red slimy mat or sheet that covers the LR or substrate.
Red slime algae will also grow on almost any stationary object in a tank and sometimes appears as a blue-green or dark red color.
Red slime algae are not algae at all but rather a type of bacteria (Cyanobacteria). Cyanobacteria can be killed using an antibiotic but this will also kill some beneficial nitrifying bacteria as well. It is always better to find the source of the problem anyway.
Unlike hair algae red slime generally like areas of the tank with low light and low current flow.
Bubble Algae:
Usually appears as little green bubbles on LR.
The bubbles will continue to grow until it breaks down and releases hundreds of tiny spores in the tank creating much more bubble algae.
This is why extreme caution should be taken if trying to remove the bubbles by hand.
If you do try this method have a siphon going close by the bubble in case it bursts during the attempt to remove it. This way there is a good chance a majority of the spores will be sucked up through the siphon.
What causes algae blooms?
Phosphates:
One of the most important nutrients for algae growth is phosphate. Eliminating phosphate in the aquarium is the number one means to prevent algae blooms.
The most common source of phosphate in the aquarium is untreated tap water. Other sources include food, some salt mixes, and some additives.
Nitrate:
Nitrate is another important nutrient for algae growth.
Nitrate can build up in many tanks as the by-product of nitrite decomposition.
Studies show that as much as 90% of the food given to your fish can end up as nitrates. Over feeding can be a major factor of high nitrates. Other sources include untreated tap water, some salt mixes, and some additives.
Dissolved Organic Matter / DOC:
Dissolved carbon is another source of nutrition for algae.
Unfortunately unlike the phosphates and nitrates mentioned above there is no easy way to measure the DOC concentration in the aquarium.
The best means of controlling DOC is through the use of a protein skimmer.
Silicates:
This is the compound required by diatoms for growth. If there are no silicates in the water there will be no diatoms.
Common sources of silicates include tap water, play sand that contains silicates, and the curing of LR.
Lighting:
Improper bulbs with a K value less the 5000 will almost always promote algae blooms.
As bulbs age the K value decreases as well. As a general rule of thumb MH bulbs are changed once a year and fluorescents every 6 months. I don’t like general rules of thumb however and find it best to use your judgment.
If there is a sudden algae bloom in your tank and the bulbs haven’t been changed in a while this could very well be the cause.
Carbon Dioxide:
An often-overlooked source of algae.
The main source of a high C02 level is poor circulation in the aquarium.
Try to avoid any dead spots in the aquarium. These are often found around or inside of LR formations where there is very little to no circulation.
An easy way to check if C02 is accumulating in the tank is to take a sample of about a half-gallon from the tank and vigorously aerate for 24 hours. Now check the pH level of the sample and from the tank at the same time. Compare the two results and if the pH of the sample is greater then 0.2pH units of the tank then the tank is probably accumulating C02.
Thing that can be done to avoid algae problems.
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. />
As mentioned above 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
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