The comprehensive guide to marine algae


1. Understand Algae and why it occurs

All algae requires light to photosynthesise and nutrients on which to feed. Different types of algae prefer different levels of light and different nutrients. It is true that any body of water suitable for maintaining aquatic life will also offer a suitable home to some of the thousands of species of algae.

Even the cleanest looking aquariums and ponds will contain some algae, it is inevitable! So this is a guide to control the growth of algae, it is normally possible to retard its spread to the point that it is no longer visible or of concern.

Always remember that out of control algae will not harm your fish. It is in fact a symptom of underlying conditions that will actually aid water quality until better conditions are restored. At this point the level of algae will naturally reduce.


2. Lighting can be used to fight algae

Or rather a lack of lighting or the correct lighting! Most common forms of algae require continuous lighting to photosythesise. Broadly speaking most algaes will not start to multiply until they have been exposed to light for a period of 2-4 hours. For this reason we recommend in most instances using a light timer and running the lights for 4 hours on, 2 hours off, 4 hours on. This is not including blue lighting used in the early mornings and evenings. The blue light spectrum is much less useful to most types of algae and therefore less of a concern. When following this advice in a reef tank it is worth considering certain corals and invertebrates do require longer periods of continuous lighting. In this instance it would not be suitable to introduce a break in the aquarium lighting.

The quality of the light is also important, older tubes that need replacing will over time change in colour spectrum and so regularly replacing your tubes will ensure the correct light is being used.

NOTE: Any aquarium that receives direct daylight, or bright in-direct daylight will struggle with algae problems and should be relocated. Ideally all aquariums should be sited away from natural light sources.


3. Do I need to water change more?

Water changing is not always the best answer to any given problem but in almost all cases it will help. There are a variety of ways to reduce the build up of undesirable nutrients and chemicals in an aquarium, however none are as instantly effective as a water change. This is becasue a water change will immediately dilute the effects of a problem whilst its route cause is addressed.

Long term you can gauge frequency and quantity of water changes by testing the Nitrate. As Nitrate is an end product of biological filtration it will only ever increase in between water changes. Test the Nitrate before each water change, if it is higher than the previous water change either change a higher % of water or preferably schedule water changes more frequently. On average look to change around 10-20% each time. Never more than 25% unless unexpectedly poor water quality needs correcting rapidly.
Nitrate is important to monitor. Almost all nuisance algaes will be stunted if the Nitrate in an aquarium is maintained below 10-15 ppm.
4. What about phosphate?
Phosphate is crucial to certain types of algae and if reduced to effectively zero will remove these algaes ability to grow. Most algaes will feed from phosphate but only the types dependant on it can be controlled by removing phosphate alone. One of the most common nuisance marine algaes is hair algae. The good news is that this will find life extremely difficult, often dissapearing from view altogether if Phosphate is managed very strictly.


5. Fight Algae with Algae

All types of algae do a useful job, but more than that some are very attractive. In a marine aquarium deep red/purple coraline algae looks stunning. Technically not a true algae as it requires a calcium based structure to maintain its form. It will however use many of the same nutrients as nuisance algaes. A healthy spread of coraline aglae will often fight hair algae for space – and can win.
Similarly, growing concentrated algae in one area away from the main aquarium (A refugium), for example in the main or an additional sump tank, can be very effective. The prinicipal is simple, no matter what the water conditions a given aquarium can only ever support so much algae. Ultimately the algae will exhaust its own food source and cease to multiply. By creating an area in which the algae can live most easily, you create an area in which it lives almost exclusively. The intended growth point is made more attractive by using plant friendly 24 hour lighting. Typically a high intensity lamp mounted close to the surface of a shallow tray of water. The concentrated light will stimulate the algae to absorb nutrients at a faster rate than any algae trying to grow within the aquarium itself.
As an added bonus algae promoted within the filter system becomes a natural nitrate filter.
6. Temperature
If your aquarium temperature regularly soars above the intended level then algae will flourish. By keeping your tank water regulated to a cool consistent temperature with the use of a chiller or fans you will be limiting one of the growing factors.
Remember its not just the outside air temperature that will heat up your tank, if you take measurements throughout the day you may find that your aquarium lighting is regularly heating the tank above your preferred level.


7. What about my protein skimmer?

The more effective your protein skimmer, the more organic material it will remove before it can break down into nutrients the algae can use. General water quality is improved with stronger skimming. All skimmers are not equal, those that feature needle wheel impellors will remove the broadest range of organic pollution.
It is of course possible to run a marine aquarium without a skimmer, nature does offer its own solutions to build ups of proteins and other organic matter. Algae is in fact one such solution – for those not using a skimmer the algae refugium solution explained above is a way of working with nature to benefit from the positive influence of algae.


8. What eats algae?

Many grazing invertebrates will eat algae. However this is symptomatic treatment and therfore ignores the underlying issues. Generally the effectivness of tank grazers is also a let down. For example a grazer will tend to eat the easiest areas of algae and move on, this serves only to trim the algae. The biggest downfall of grazers is the volume needed to be effective adds an extra load on the tank. Also whatever made the algae grow either passes straight through them and it grows again. Worse still some, particularly urchins and nudibranches store minute toxins formed by the algaes and release them in concentrated form upon death.
To summarise; its nice that turbo snails and hermit crabs help to tidy the tank, but ultimately you should rely upon other methods if you have an algae problem.


9. What should I be aiming for?
This list is not exhaustive but anyone who maintains these low levels will make it impossible for algae to get out of hand.
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate 15ppm or less
Phosphate 0.015 mg/l or less (most test kits would read this level as zero)
Lighting no more than 12 hours per day max. Ideally 8 hours with a 2 hour ‘siesta’ break in the lighting midday.
Constant aquarium temperature suited to the inhabitants not the algae


10. Red/Brown slime algae

Characterised by its rapid spread over pretty much any surface in the aquarium. This form of algae is very common in new marine aquariums. Typically it occurs shortly after adding the first livestock (including living rock) and will naturally subside as the tank matures. These algaes feed from Nitrite which is more prevelant in new aquaria. As the filter matures Nitrate will be reduced to an effective zero, thus removing this type of algaes food source. Slime Algae also perfers low lighting, often it will be replaced by coarser algaes in new aquaria with powerful lighting.

If Slime algae continues for more than a few weeks after livestock has been introduced it is often symptomatic of other problems that have stopped the aquarium maturing correctly. In the first instance check the Nitrite and Nitrate levels of the aquarium.
If the water quality is fine and slime algae continues long term but only in certain areas of the aquarium it is likely due to a low flow rate, ‘dead spots’ in these areas. The use of powerheads will not only help retard the algae growth, general good movement of water helps to maintain a cleaner aquarium all round.
Slime algae is easily removed in the mean time by siphoning using a length of tubing (no need to use a gravel cleaner attachment for this job).


11. Hair Algae

The type of algae we are asked most about here at Warehouse Aquatics! Different species grow tenasciously in both fresh and saltwater. Luckily hair algae is highly dependant on phosphate. High phosphate will result in the algae spreading rapidly on to every available surface. Frequent water changing will reduce phosphate dramatically (assuming the new water itself does not contain high levels of phosphate – tap water often does) and this will reduce the growth rate of hair algae. This makes it manageable to pull out of the aquarium.
It is possible to actually stop the algae altogether. Hair algae only needs tiny amounts of phosphate to grow very slowly but it is still dependant on those tiny amounts. Using a phosphate scrubber such as the highly regarded Rowaphos along with good quality RO water makes it possible to maintain very low phosphate levels.
This will steal the algaes crucial food source and once removed will not grow back.
Note: despite the algae no longer being able to grow it will take a very long time to die back. It is faster to remove what remains by hand or introduce algae grazing invertebrates.
Phosphate removers can either be placed in a media bag inside your filter or sump, or for optimum effect used in a fluidised reactor. Remember to check phosphate levels regularly and as soon as they start to climb replace or renew your phosphate removing media.

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