Dinoflagellates in a Saltwater Aquarium

Dinoflagellates in saltwater aquariums

What are Dinoflagellates in saltwater aquariums?

Dinoflagellates also known as armored flagellants , are a sub-strain that predominantly includes single-cell organisms with two distinguishing flagella during the mobile life cycle, chromosomes that are condensed during interphase, and the absence of histones.

The bulk of the dinoflagellate lives in the sea water and is there much of the phytoplankton is.

The dinoflagellates occurring in saltwater aquariums are mostly reddish or brown in color.

How to detect dinofragellates in a saltwater aquarium

You can easily detect the presence of dinofragellates by looking at the appearance.

  • The red-brown color of the evidence indicates dinoflagellates
  • No permanent chaining, so no solid “carpets”
  • By waving your hand over the dinoflagellates, these dissolve and the water (depending on the infestation) is slightly rust-colored
  • After 10 minutes it is it is as if you had never wagged in the aquarium!
  • Significantly less in the morning and increasingly stronger infestation during the light phase
  • After a water change, the dinoflagilates tend to be more than less
  • Water “smells” penetratingly (depending on how violent) – Gas inclusions, optically like the cyanobacteria, but much less
  • This alga is microscopic and easy to recognize

Dinoflagellates in saltwater aquariums and their side effects

  • Unsightly toppings
  • Cloudiness in the pool water
  • Damage from toxins up to life-threatening effects for pool residents, ingest the dinoflagellates as food. Lower organisms such as snails, worms, starfish, sea urchins … are particularly at risk.
  • Coverings cover surfaces / corals and damage them by depriving them of light
  • Clogging of mechanical filters, overflows and skimmers
How I Beat Dinoflagellates

What causes the excessive occurrence of dinoflagellates?

Basically, there is a small number of dinoflagellates in almost all tanks.

Dinoflagellates can also be created by introducing corals, living stones or specifically can also be brought in by so-called live sand.

Dinoflagellates are particularly common in pelvises that are still young. This is because the existing settlement area is not yet of desirable Bacteria / algae is ingested, and these algae then unintentionally spread strongly.

The prevailing conditions in the aquarium decide whether Dinoflagellaten through Colonization with other algae or bacteria can be suppressed or whether it is by being ideal for them Conditions, even a strong increase occurs.

Suboptimal design of the pool and the lack of a suitable cleaning crew leads unfortunately to this dreaded plague occurs again and again in saltwater aquariums.

Main problem: under favorable conditions, dinoflagellates can separate extremely quickly and multiply. In this case, it becomes a dinoflagellate infection.

How do dinoflagellates infect the saltwater aquariums?

  • The first attacks usually take place on the coral sand.
  • In a very short time, the infection spreads to the rest of the decoration and also begins to overgrow corals.
  • The multiplication of dinoflagellates takes place not only on decoration, but also in open water.

Overview of the top 10 measures of preventing dinoflagellates and their effects (Table)

Increase in pH value not very effectiveThe sole increase in pH has only a limited effect and for some Dinoflagellate species
Reduction of pH valueno effectSole reduction of the pH value only affects a few Dinoflagellates have an influence and even there only to a limited extent
Reduction of CO2 concentration due to increased pHslight improvementIntake of CO2 is a must for purely photosynthetic organisms. If the pH value is increased while the alkalinity remains the same. The CO2 concentration decreases (a pH value higher by 0.3 leads to a 50% lower CO2 concentration).Some aquarists report the success of the method,others do not
Manual removal by Suctionnot very effectiveEffect is only limited in time. If the population is reduced, however, it will not be destroyed
Reduction the lighting durationslight improvementEffect is usually only limited in time and does not lead to death. Also harms other pool residents
Reduction of nutrients such as nitrates and phosphatesslight improvement, improvementThe greater the reduction and thus the lower the concentration, the more effective! Low phosphates concentration is more effective than low nitrates concentration
Silicate contentimprovementIncreased silicate concentration triggers diatoms and is repeatedly seen as a possible trigger of so called dinoflagellate infections. Presumably, this also improves the chances for one Dinoflagellate population
Increased use of coal or ozoneimprovementNo influence on dinoflagellate population but it improves the chances of survival of the pool inhabitants because toxins are filtered out
Competition for settlement area through introduction of other bacteriaGreat improvementDisplacement tactics – minimal effort with no negative side effects. Does not work with severe infections and often requires optimization of the pool / technology
Use of cytotoxinsGreat improvementSide effects on other living beings. Destruction of other desired algae
Dinoflagellate infection

Methods of eliminating Dinoflagellates from saltwater aquarium

Method 1: Elimination of a dinoflagellate infection by displacement with bacteria

This method has no negative side effects. It is recommend that you should try this method first before trying more drastic methods.

Successful application should even result in a more stable running pool with reduced nutrient content (nitrate, phosphate).

However, this method only has a real chance of success if the infection is not too far advanced AND the affected tank can be salvaged.

Is your tank prone to Dinoflagellate Infections?

The following facts favor infection:

  • Are there areas in the tank (especially on the bottom but also on the reef structure) which have not been cleaned properly? Can you even find places where sludge collects (rotten corners)?
  • Is your tank missing suitable “floor cleaning organisms”, which can clean the sand?
  • Leftover food / sludge rummaged through?
  • Are you unsure whether the nitrogen cycle is working? This could be an indication mainly of excessive nutrient values (nitrate, phosphate)

How to get rid of dinoflagellates infection by displacement with bacteria

The most important thing: First make sure that all parts of the tank are properly flooded through.

1. Install floor cleaning inhabitants in the tank
a. To clean the surface of the substrate:

Gobies of the genus Valenciennea and im are particularly well suited / industrious special V. Sexguttata and V. Puellaris as well as A. Phalaena.

Note: The first two genera in particular are very shy.

b. To burrow through the substrate itself:

Examples of well suited inhabitants are: burrowing starfish, sand dollars and Babylonica snails

Important: Do not use digging starfish in tanks that are still very young, as these find no food there and starve to death.

Attention: When buying the animals, make sure that the pool is large enough. Also take into consideration conditions and compatibility with the existing pool.

2. Ensure that there are conditions to prevent dinoflagellates infection from worsening
  • Reduce the light interval during treatment to a maximum of 6 hours / day (HQI or daylight / neon tubes such as T5, blue light phase can be longer)
  • If the pool is illuminated in some other way (sunlight, ..), it should shielded (masking the panes with UV-impermeable film)
  • No water changes during treatment
  • No addition of trace elements during treatment
  • If possible, introduce little / no further nutrients into the pool
3. Vacuum infested areas and inoculate the substrate with nitrifying bacteria

(Particularly suitable: RED X (Fauna Marin) CyanoClean (Korallenzucht.de)

Dispose of the pool water necessary for suction and with fresh salt water refill.

Optimal time: in the evening, shortly before the lights are switched off.

  1. Prepare low-dose bacterial solution from some pool water (e.g. 500ml) and a nitrifying bacterial culture. Let the prepared, low-dose bacterial solution rest for 1 hour at room temperature.
  2. Inoculate using a larger syringe without a needle – Inject approximately 1ml of the diluted bacterial solution approx. 5mm deep into the substrate in as many places as possible that were previously covered with dinoflagellates.
  3. Let the skimmer run 24 hours a day to remove any bacterial blooms and thus connected to exclude insufficient oxygen supply!
4. Feed the bacteria with the bacterial nutrient solution or something similar

Follow the dosage according to the manufacturer’s recommendation.

5. Now check more frequently the nitrate / phosphate values with high-quality test kits that measure / display accurately in the range close to 0mg / l

A reduction of previously increased nitrate and phosphate concentration is common and desired with this method. However, countermeasures must be taken if this occurs too quickly or to 0 values

Does the reduction in values take place very quickly?

  • Reduce the dosage of bacteria and the feeding (Some coral species are sensitive to this actual improvement)

Do the values reach the no longer detectable range?

  • Reduce the dosage of bacteria and the feeding
  • Feed more, eg with unwashed frozen food
  • With SPS / LPS population in the tank: dose amino acids for feeding
6. Repeat suction, inoculation & feeding in a 1to 2 day rhythm until the toppings are gone.

This can take a few weeks, depending on the severity of the infestation.

Dinoflagellate infection

Method 2: Elimination of a dinoflagellate infection Dino X / phycoEx

In the case of stubborn infections, consistent use of Dino X or phycoEx is recommended

Both products presumably have identical ingredients and are effective against dinoflagellates as well as other types of algae.

The remedy is probably a special cell poison and does not use antibiotics.

How to get rid of dinoflagellates infection using DinoX / phycoEx

Follow the dosage instructions consistently

  • Always in the evening, approx. 1 hour after the lighting has been switched off dosage 5ml per 100 liters of aquarium water (max. 6ml / 100L), directly into the tank
  • Repeat the dosage every 2nd day until it is successful
  • Reduce the light interval during treatment to a maximum of 6 hours / day (applies to HQI such as T5 / T8, LED, blue light phase can be longer)
  • If the pool is illuminated in some other way (sunlight, ..) shield e.g. by masking the panes with UV-impermeable film
  • Set the skimmer well (Increased skimming due to the death of the dinoflagellates / other algae)
  • No water changes during the treatment
  • No trace elements added during treatment
  • If possible, introduce little / no further nutrients into the pool
  • No OZONE or carbon during the treatment (removes the chemicals!)
  • No PO4 / silicate absorbers, use during treatment (removes the chemicals!)
  • Switch off the UV clarifier during treatment (inhibits the effect!)

Method 3: Eliminate dinoflagellate infection by combining several measures

If you want to avoid the use of medication (Dino X / phycoEx), you can do so here

  • Take measures (see below) to reduce the nutrients in a very area close to 0 mg / l so:

– Phosphate concentration (PO4) → ~ 0mg / l

– Nitrate concentration (NO3) → ~ 0mg / l

  • Do not add any new nutrients, trace elements or amino acids
  • No water changes
  • Silicate concentration in the pool → 0 mg / l
  • Raise the pH value and keep it at 8.4 and 8.5 → Add lime water. If there is no improvement after a few days → increase the pH value to 8.6.
  • pH >> 8.6 should be avoided in order not to expose animals to unnecessary stress. Maintain alkalinity or keep it at a high level (but ≤ 12 ° dkH).
  • Reduction of the lighting duration (HQI, T5, T8) to a maximum of 6h / day (Blue light illumination time can be longer)
  • Vacuuming the coverings to reduce population density and reduce toxicity
  • Measurement of the water parameters is essential with this method.

– Use high quality tests to assume correct readings. As previously recommended, leave all animals in the pool.

– Conditions in the replacement pool are usually worse than in the main pool

– Risk of infection of other pelvis with dinoflagellates

– Risk of re-infection of your own pelvis when you move back from a replacement pool

How to beat dinoflagellates in a saltwater aquarium

Method 4: Nutrient reduction

Reduce the phosphate concentration

a) Reduce phosphate input

  • use phosphate-free feed,
  • Wash out frozen food well with water
  • Generally use high quality phosphate-free salts and additives

b) Break down phosphate

  • stronger skimming
  • Mud filter or refuge with macroalgae (MiracleMud)
  • Add suitable bacterial cultures
  • Use phosphate adsorbers
  • Macroalgae in the pool

Reduce the nitrate concentration

a) Introduce less nitrogen

  • Only use fresh water without nitrate pollution use a reverse osmosis system or demineralizer for source water with a high nitrate content
  • feed less
  • Reduce temperature
  • Remove dead organisms from the tank as quickly as possible
  • Remove dirty corners
  • Good current everywhere in the pool
  • Reef washout
  • Reduce bio balls / biological filters, clean frequently

b) Nitrate breakdown

  • Skimming or increasing the skimmer performance
  • Keeping and harvesting macroalgae (Caulerpa, mud filter, ..)
  • Add suitable bacterial cultures
  • DSB (deep sand bed)
  • Deltec nitrate filter

Reduce the silicate concentration

a) Keep the output water free of silicates

  • Use resin-based silicate / silica filters (ultrapure water filter) – Attention: regular checks and then resin replacement necessary
  • Water demineralizer for water treatment

b) Bring the silicate absorber into the circuit

  • Absorber granules in bags or filter columns (Silicarbon, UltraSil, etc.)

Method 5: Using UV-C on the Dinoflagellates in saltwater aquariums

UV-C sterilizers use the destructive effect of UV radiation at 253.7 nm on bacteria, viruses, spores, germs and parasites.

This has no negative impact on useful nitrification bacteria in seawater aquariums , as they mainly settle on the decoration, in the substrate or on the filter material .

In microorganisms, the UV radiation changes the DNA so that they can no longer multiply.

This effect can be used to combat dinoflagellates.

In order for the maximum radiation output to be achieved, the amount of water flowing through per hour (dwell time) specified by the manufacturer must be adhered to by the UV-C sterilizer .


  • If the water is passed through the UV-C sterilizer too quickly, the irradiation time (dwell time) is shorter. This leads to a significantly poorer irradiation result. You should therefore operate the UV-C sterilizer with a separate pump that is precisely matched to the recommended flow rate – and not switch it to bypass. 
  • Also important for the retention time of the water: the container volume of the UV-C disinfectant. The larger the container, the longer the water stays in it. 
  • For the disinfecting effect, apart from the radiation power and the radiation time (residence time), the nature of the water is important.

Method 6: Lime water method for for inreasing the pH

An additional and effective method of combating an infection with dinoflagellates in a saltwater aquarium is to increase the pH value .

You can easily increase the PH by adding lime water.


  • It is important here that the pH value is raised slowly and not too quickly. The recommendation is: increase the pH value by 0.1 per day
  • A value of 8.5 has proven to be very effective as the upper limit for the pH value in daily practice 
  • If the pH value is increased with lime water, it is important that the pH value is measured regularly and counteracted in good time if the increase is too great
  • In seawater aquariums where a calcium reactor is in use, another important method to increase the pH value is to let the outflow water from the calcium reactor run over coral fractures again to neutralize any free Co² that may still be present .

How to prepare lime water for increasing the pH

Dosage instructions

Lime water = 1 tablespoon (~ 15 ml) calcium hydroxide per 5 liters 0.15% of the tank volume addition of lime water

→ increase the pH value by approx. 0.1 pH (depends on the ecosystem)

To produce lime water you need calcium hydroxide (Ca (OH) 2 ) and a sealable vessel to mix the solution.

  • Fill the vessel with tap water
  • Add 1.5 g calcium hydroxide per liter of tap water. You must avoid a higher dosage, as only about 1.5 grams of calcium hydroxide dissolve in 1 liter of water
  • Then close the container and shake it tight

(Attention: calcium hydroxide is very corrosive, always observe the processing instructions on the manufacturer’s packaging!)

  • After a while, the undissolved calcium hydroxide settles on the bottom of the container and a clear solution is formed above it
  • It is important that the sediment of the mixture does not get into the aquarium circuit


  • Now the lime water can be added drop by drop into the filter tank – not directly into the aquarium!
  • Because of the high pH value (approx. 12.5), corals and fish suffer severe burns in direct contact.
  • The solution should also not be added to the water in the suction area of ​​pumps, as this would quickly lime scale
  • Choose a container that can be closed with a screw cap and use a finely adjustable tap for dosing
  • The lime water can only be kept if the container is hermetically sealed.
  • If the CO 2 from the ambient air combines with the lime water, this precipitates as insoluble lime and can no longer be used for the intended purpose

Useful to remember

  • The pH value will usually decrease again quickly, which is why dosing several times a day is necessary. The pH value should be checked at least in the morning and evening. Depending on the measured value, lime water has to be added.
  • Slowly add the lime water to the pool.
  • Good ventilation lowers the pH value, and may therefore be counterproductive for the treatment. Temporary reduction in ventilation is one way of compensating for this.

Side effects

  • Precipitation in the pool and deposits on objects (flow pumps, pump wheels, overflows,) can occur.
  • Calcium concentration and alkalinity will also increase. Combined with the higher pH value, this should stimulate the calcification process of stony corals, so it is more positive.
How I Defeated Marine Dinoflagellates in 10 days

Method 7: Eliminating dinoflagellates in saltwater aquariums with chemical agents

Another way of combating dinoflagellates in saltwater aquariums is the use of chemical agents, i.e. algae control agents.

You should choose the use of such means as the last option – ideally after you have exhausted all other possibilities without success.

Side effects of using chemical agents:

  • In addition to the dinoflagellates, algae killers also attack and kill all other types of algae, including zooxanthellae, i.e. the symbiotic algae stored in the coral tissue
  • With more sensitive corals, this can lead to irreparable damage
  • If you use an algae refuge that is occupied with caulerpas, you should be aware that the treatment will also kill the algae in the algae refuge
  • Sea urchins and starfish have a high level of intolerance to algae killers


  • If you decide to use an algae-killing agent, do not filter through activated carbon during the addition, as this will otherwise be withdrawn from the aquarium water by the activated carbon
  • Only after the treatment has been successfully completed does the algae destruction agent need to be removed from the aquarium water with activated carbon

Summary of dinoflagellates in saltwater aquariums:

You can easily avoid a severe infestation of dinoflagellates in a saltwater aquarium easily. Additionally controlling an infestation is also possible if you take the following measures:

  • Check whether there are dinoflagellates on purchased live rock or on the substrate rock of newly acquired corals, if so, these must be removed without residue and, if in doubt, not introduced into the aquarium.
  • Stop supplying trace elements and do not change the water
  • Suck off dinoflagellates regularly and filter the sucked off water through a micro-fleece. The filtered water is then returned to the aquarium
  • Use of UV-C sterilizers
  • slow increase in pH
  • Use of algae killers only if you have exhausted all other options without success

Dinoflagellates Complete Profile

FeatureDinoflagellates Detail
Basic characteristics• There is an extremely large variety of shapes within the dinoflagellates. However, these can be viewed as modifications of a basic form.
• The size ranges from 2 µm ( Gymnodinium simplex ) up to 2 mm ( Noctiluca miliaris ), with most species between 20 and 200 µm in size.
• The shape of the free-swimming cell (mastigote) is egg-shaped to rounded, with the anterior usually more pointed than the posterior.
• The dinoflagellates have two long flagella , one pointing backwards (transverse flagella) and the other strikes in a plane perpendicular to it (longitudinal flagella). This arrangement of the flagella is called dinokont.
• A furrow, the so-called belt (cingulum) runs around the cell and divides it into an anterior (episoma) and posterior (hyposoma). If there is a theka, the parts are called epitheka or hypotheka.
• Another furrow, the so-called sulcus, runs to the posterior.
• The transverse flagella strikes in the cingulum, the longitudinal flagellum in the sulcus.
Distribution and habitats• Dinoflagellates are cosmopolitan in salt water as well as in fresh water and can colonize many habitats there due to their wealth of shapes. Around 90% of all species are assigned to marine plankton, with the greatest biodiversity in tropical waters.
• They are also benthic creatures and also penetrate the sediments. They can also be found in the polar region or in sea ice.
• Fewer species are common in freshwater. By 1970, 220 freshwater species had been described that inhabit lakes, ponds and moors around the world. The distribution area extends roughly from the equator to 78 ° north latitude (Spitzbergen (island)).
• The differences in altitude range from -209 meters in Israel to 4150 meters in the high mountain lakes of Mexico.
• Since some species enter into symbiosis or live as parasites, living things are also used as habitats. For example, dinoflagellates live as endosymbionts in many corals and are then referred to as zooxanthellae.
• Autotrophic species are dependent on light-flooded layers of water, heterotrophic species can also penetrate into completely dark depths.
Nutrition• About half of the dinoflagellates are autotrophic and can use inorganic carbon with the help of assimilation of the chloroplasts.
• Almost all photosynthetically active species are auxotrophic and require vitamins (cobalamine , biotin , thiamine ) for catalytic purposes. These are absorbed via phagocytosis.
• Autotrophic species also enter into a symbiosis with cnidarians (Cnidaria) in particular corals, molluscs (Mollusca) but also foraminifera (Foraminifera) and ciliate (Ciliata).
• Heterotrophic dinoflagellates feed on a wide range of planktonic organisms that nanoplankton to large diatoms enough. This also includes dinoflagellates of our own and other species, detritus and even eggs and larvae of copepods .
• In the simplest case, the food is ingested by phagocytosis (for example Noctiluca miliaris).
• Due to special cell structures such as peduncles or pallium, heterotrophic dinoflagellates can also feed on organisms that are many times larger than themselves (for example Pfiesteria or Protoperidinium).
Bioluminescence• Some species are capable of bioluminescence. The glow is a response to mechanical stimulation.
• In nature, these are deformations of the cell membrane that are caused by shear forces. Heavily churned water such as breaking waves or fast swimming fish can trigger such stimulations.
• The emitted light is blue-green and has a maximum at 474-476 nm.
• Presumably, enemies will be deterred by the flash of light. As with almost all types of bioluminescence, this is due to a reaction between luciferases and luciferins.
Genetics• Dinoflagellates have unique properties within eukaryotes.
• The chromosomes are also condensed during the interphase and are visible in the electron microscope.
• The chromosomes form a garland structure, with the individual fibrils only 2.5 nm in diameter, which is due to the lack of histones.
• The remaining eukaryotes have fibrils ten times the diameter with a central nucleohiston strand.
• The modified base hydroxymethyluracil (HOMeU) is only detected in the DNA within the dinoflagellates. With a total proportion of 4-19% it replaces 12-70% of the thymine bases.
• The number of chromosomes varies between 5 atSyndinium turbo and 274 in Ceratium hirundinella.
Autotrophy• Basically, dinoflagellates can accommodate very different plastids that differ from the basic type. This is due to phagotrophy which is also maintained in autotrophic species. This led to another, tertiary endocytobiosis in the tribal history.
• The ingested organisms can come from different groups, such as Haptophyta , Cryptophyceae , Heterokontophyta or a chlorophyte.
• The chloroplast, which originally came from the red algae , is completely or largely regressed and in the latter case appears as an inactive eye spot (stigma). Occasionally there is also a in the chloroplastNucleomorph included.
Toxins• Some species produce extremely potent poisons. The saxitoxin example is from members of the genus Alexandrium (
• Gonyaulax produced).
• When poisonous species multiply on a large scale, so much poison is produced that fish and other marine life are also killed [5].
• Karenia brevis produces brevetoxins, and the “red tides” they generate can lead to mass deaths in fish, birds and mammals.
• The disease Ciguatera, a type of fish poisoning, is caused by metabolic products of the species Gambierdiscus toxicus.
• The dinoflagellate toxins ciguatoxin and maitotoxin get into fish via the food chain, which also become highly toxic. The poisoning can be fatal in humans.
• The toxin from Pfiesteria piscicida, on the other hand, is not accumulated via the food chain, but is directly toxic to fish and humans.

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