Glass anemones are the most common pests. It's almost impossible to set up an aquarium without introducing them. They often attach to live rock or on frag plugs.
A single glass anemone may not cause much harm, but they quickly multiply. By cutting off a part of the foot, identical small glass anemones form. The tentacles of these creatures can sting strongly, causing injury or death to corals.
Removing them with a sharp knife often yields the opposite result. Small remnants may remain or drift through the tank, giving rise to new glass anemones.
Glass anemones can be controlled with vinegar. Inject a small amount with a syringe into the foot or mouth. This may need to be repeated.
It is also possible to control them in a biological way. Peppermint shrimp eat small glass anemones, but only when they have little other food available.
Filefish and coral butterflies are often more effective, but these animals also target coral polyps and buttons.
Split anemones often come with live rock. They are thicker than glass anemones and have shorter tentacles. Usually, they turn bright green under blue lighting.
Split anemones are named for their ability to split rapidly. They can form a plague in a short time. Like the glass anemone, the split anemone stings its neighbors.
Removing them is often easier than with the glass anemone. Once injected with vinegar, the split anemone quickly releases and can be caught with a net.
Some coral butterflies also prey on them. However, they often target coral polyps as well.
The mantis shrimp: loved by some, hated by others. These creatures come with fresh live rock and can vary in size.
They range from 2 cm to 30 cm, although the latter is not often encountered. There are two types: "smashers" and "spearers," which are further divided into various species, each with its own behavior.
Not all mantis shrimp are harmful. A small specimen in a tank with large fish will likely cause little damage. Conversely, a large specimen with small fish can quickly empty the tank. Spearers are also more adept at hunting larger fish than smashers.
The difference between a spearer and a smasher lies in how they catch their food. A spearer has a spear-like appendage on its legs, with which it can catch swimming fish. A smasher has club-shaped legs that can exert tremendous force on its prey.
Catching these creatures is not always easy. Crab traps or traps made from a empty bottle may work. Sometimes a net or removing the entire rock where it resides works better.
After capture, consider not killing them immediately. It is very interesting to keep them in a specially designed nano tank. Otherwise, there are many enthusiasts on various forums who would gladly take them off your hands.
Feather Duster Worm
A feather duster worm is a small sea star. It feeds on short algae and detritus. In itself, this is not a problem, but they can reproduce very quickly. Shedding an arm creates a new feather duster worm, and this happens rapidly.
Feather duster worms can suffocate corals if they are massed on them. There are also reports that some types eat buttons.
The best way to remove these animals is manually. They are easy to catch. The help of a harlequin shrimp can also be sought. These are beautiful shrimp that are best kept in pairs. Remember that the harlequin shrimp only eats sea stars. It prefers the large fleshy Linkia or sand sifting stars over the small tough feather duster worms.
These shrimp should also be supplemented with (frozen) sea stars.
Myrionema is, in my opinion, the worst plague there is. Glass anemones, split anemones, feather duster worms; there are natural enemies for everything. Not for myrionema, at least not those that fit in an aquarium.
Myrionema looks like a mat of fuzzy polyps. Close-up, they resemble small palm trees. Sometimes they retract, forming only a mat of small black dots. The "palm trees" are interconnected by a root-like structure. This is often deep in the rock, making picking myrionema almost pointless.
Another drawback of picking is that if a single polyp blows away in the current, a new field may emerge. Vinegar, boiling water, or a strong lime solution do not yield satisfactory results. Covering with aluminum foil may sometimes work, but this can be toxic to other animals.
There are reports that the fire sea urchin, Asthenosoma varium, eats this plague. However, it becomes quite large and is also poisonous.
Unfortunately, the only effective solution is to remove the contaminated rocks.
This is one of the most challenging algae to remove. It looks like small feathers connected by a common root system.
The best results have been achieved by raising the Kh to 12. Most of these algae disappear then. The sea slug Elysia viridis also eats these algae. The downside is that the slug does not survive if it runs out of algae.
These slimy algae form a film over everything. They are brown to golden and often contain air bubbles. These algae arise from an excess of silica (silicate). This is present in tap water and is not removed by a reverse osmosis unit.
Natural seawater can also contain a lot of silicate. A silicate filter can be a solution in this case. I use Anti-phos, which also contains a silicate remover.
Red Slime (Cyano-bacteria)
This is not actually an algae. Red slime, as well as purple slime, are cyanobacteria. These bacteria produce a slimy, sticky substance to protect themselves from bright light. The amount of slime will decrease at night and increase during the day.
The problem that allows the slime to thrive is a lack of circulation. Also, animals that disturb the substrate (sea stars, strombus snails, hermit crabs) prevent slime from taking hold.
This seaweed is a calcareous algae, so it requires a lot of calcium. Some aquarists struggle to make it grow, while others find it overgrowing their tanks. Many aquarists consider this seaweed decorative and can be kept in check by regular pruning.
The obtained bunches can be exchanged for cuttings. I am not aware of any animals that eat this seaweed. A decrease in Ca will cause this seaweed to stop growing or decrease. This also means that corals will stop growing.
Red Hair Algae
This starts as a decorative pile of red fuzz but quickly grows into a true plague. Manual removal works best; the fuzz is not firmly attached. The cause of these algae is still not entirely known. They are said to require high concentrations
of iron, as well as phosphate and nitrate. Some sea urchins and rabbitfish eat them, but this varies by individual.