Reef Aquarium Synopsis

Parasites, Problems and Practices

By: Glenn

joanallanaeIn the hobby, the reef tank is the final obstacle the advanced aquarist attempts to conquer. In most aquarist’s view, the reef is the most diverse and the most complex, because we are creating an ecosystem. This ecosystem, as in the wild, has fine lines between success and failure.

Ecology teaches us if a closed ecosystem surpasses (carrying capacity) one or many species will become extinct were a different species favoring the new variables flourishes. The same holds true in our “closed ecosystem.” It is the aquarist’s job to keep all species in check.

In the reef tank, there is limited space for invertebrate “housing.” We need to keep unwanted pests in check. We cannot afford, with the price of live rock and reverse osmosis units, to let our ecosystem fail due to overpopulation of algae, planaria or Aiptasia.

In this synopsis, I will discuss a few of the most commonly encountered pests attacking our closed system. I will discuss the three forms of attack on our ecosystem and explain the effect, cause and cure.

The first form I’ll discuss is passive encroachment. This is when a species dominates and pushes away a different species causing its demise by either pushing it of its own skeleton (picture 1) or by outright suffocation (picture 2). This effect occurs with algae species, which can grow much more rapidly than the invertebrate it is battling. Passive encroachment by Ventricaria ventricosa or from her in Valonia happens quickly, and, for example, can push the tissue of a Euphylia coral of its own skeleton causing recession and death. This will leave dead calcareous skeleton where phosphate can “stick” and feed the Valonia which also has a new area to grow unabated.

Next is the infamous red slime algae (Cyanobacteria) which more commonly occurs in marine fish tanks with high organic loads. We can do a seminar on Cyanobacteria alone, because almost everyone has encountered this at one time or another. Cyanobacteria grows at an astounding rate, so once it gets a foothold in your ecosystem, it is tough to beat. There are many products out there to stop it, but you must really attack the root of the problem or it will be an ongoing and usually losing battle. Cyanobacteria is always present in your system. A tiny patch may live in your overflow box unnoticed until conditions in the ecosystem favor its growth.

Causes of passive encroachment by Valonia and Cyanobacteria are:

  • Lack of circulation: dead spots, low flow, areas for detritus to accumulate;
  • High organic load: high initial T.D.S. (lack of R.O.), lots of fish, overfeeding, weak skimming;
  • Lack of herbivores: snails, hermits, echinoderms, herbivorous fish;
  • Improper lighting: incorrect spectrum (to red), too much light during initial cycle, improper bulb maintenance; and
  • Poor substrate: substrate containing too much calcareous shells where phosphate can “adhere.” Poor live sand (lots die off).
  • Cures for the passive encroachment of Valonia and Cyanobacteria in a closed ecosystem:
  • High quality water source: reverse osmosis with deionizer (low T.D.S. value); high grade salt (low in phosphate, silicates);
  • Lots of circulation: wave maker, multiple power heads, large main pump;”Good” live rock: clean (no smell), no plants or sponges, just rock and coralline, no lace or tufa;
  • High quality skimmer: tall (lots reaction time); downdraft or venturi (high turnover rate);
  • Lighting: neutral spectrum (not to red), proper hours, regular change of bulbs;
  • Lots of herbivores: snails, hermits, tangs, urchins, etc.;
  • Remove accumulated detritus: vacuum sand, clean rock periodically; and
  • Know your chemicals: calcium hydroxide precipitates phosphate; molybdenum fees algae; potassium iodide enhances brown algae.

harliquinshrimpAggressive encroachment will involve the two most common reef attackers and the most difficult to beat, Aiptasia sp. and Anemonia sp. Their resilience is due to the fact that water parameters do not matter. They thrive on the same things your coral use to live – light, nutrients and room to grow. The effect is outnumber and attack by irritation. Aiptasia have a powerful sting for their size. They can cause a coral to stay closed (picture 3) thereby causing its demise – if you can’t open you can’t feed!! The coral then dies leaving prime real estate for Aiptasia to live. Ii prettier cousin, Anemonia, looks nice, green with bulbous tips, but deceivingly stings (picture 4) and propagates even faster, taking over a tank in weeks.

Cause of aggressive encroachment by Aiptasia sp. and Anemonia sp. in a closed ecosystem: Cause is very easy in this case. It is merely introduction. Unknowingly on rock or a purchased coral, the aquarist introduces this killer into an ecosystem with all the parameters it loves, except one.

Cures of aggressive encroachment by Aiptasia and Anemonia sp. are quite simple (unlike our algae problems) — physical removal and natural predation (my favorite). Just like introducing a pine snake to control mice in a grain solo, these pests also have natural-predators or they would be taking over the oceans. The key is finding the best predator that will not harm our other invertebrate “friends.” In my 15 years of this trial and error, I will give you a list of a dozen natural predators. Some will destroy them in a few days, but as in the wild, must adapt to a new “food source” to survive. I feel all must be unfortunately “removed” to prevent predation of other species:

Chaetodon striatus
Chaetodon lunula
Chaetodon fasciatus
Chaetodon kleinii
Chaetodon auriga
Chelmon rostratus
Chelmon muelleri
Chelmon marginalus
Bergia verrucicomis
Lysmatta wurdemanni
Rhynchocinetes uritai

Lastly I will discuss a few parasites that we encounter due to live rock and coral introduction. This alone can be a ten page list, so here are the most common three I have encountered.
Asterina sp. starfish is a “cute” little white starfish that can multiply rapidly in a closed system where no predator exists. These are commonly seen before lights come on where they then scurry for shelter in rocks. They are opportunistic feeders on coral and can slowly kill and go unnoticed. Once again, physical removal and natural predation by the harlequin shrimp Hymenocera elegans can decimate an Asterina population, but once again other echinoderms are now in danger.

Heliacus sp. is a very nice looking snail, always seen on zooanthid rocks (polyps). If everyone knew how many countless hours I spend combing my polyp rocks for predatory snails, it’s a wonder anything else gets accomplished!! These “cute” snails, including Philippia and Architectonica sp., are actually like little vampires. They have a proboscis (hollow harpoon/tooth) that impales the polyp or anemone and sucks out the fluid. Physical removal is the only means – I know a natural predator must exist or overpopulation would occur I just have not found it yet (sorry!).

Lastly we will touch on a confusing one because some believe the red planaria (Convolutriloba retrogemma) is only an opportunistic feeder on autotrophic invertebrates (light- loving). The red color you see in this planaria is actually ingested zooanthellae from another invertebrate (parasitic?). Singly, they are harmless, but can quickly overtake and swarm a tank. These are easily taken under control, since they use the algae as a food source and diminish the light to slow the splitting. Secondly, sudden changes also affect planaria (temperature and salinity). Physical removal is always a great tool. Hundreds can be siphoned out with airline tubing (thereby not draining a lot of water). Lastly, my favorite, natural predation is always the finishing touch to fix the end of a problem (low planaria load, easily consumed). Here are some decent fish predators:

Macropharyngodon sp.
Anapses sp.
Synchiropus sp.
Pseudocheilinus sp.
Halichores sp.

In my experience, the best planarian eater by far is the blue/black velvet sea slug (Philinopsis sp.). This beautiful nudibranch vacuums them up as it passes over them (the planaria actually scurry away as it approaches) quickly getting the population under control. Sadly, the nudibranch is short lived so first physical removal then introduction of natural predator.

Concluding this synopsis, I only began to scratch the surface on this topic because there are many more problems and many new ways to treat them. I will never say I am the expert or the authority on any topic because I must honestly say I still am constantly learning as much from our clients as I hope they are learning from me. All I can offer is my experience and trials and errors maintaining these small aquatic ecosystems. – Glenn L.


Goemans, Bob. 2000. Marine Algae Control Secrets. Mark Weiss C.O., Ft. Lauderdale, Florida, pp. 30

Delbeek, Charles J., Sprung, Julian. 1994. The Reef Aquarium, Ricordea Publishing, Coconut Grove, Florida, pp. 291

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