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Q10180 - HOWTO: Pests in the Reef Tank, Part 1
Reef TankAnyone that enjoys gardening knows, as the garden gets better and better, the likelihood that pests will appear and upset everything increases. The same is true in a reef tank. As our level of success has increased to the point where we now can keep just about anything and even have it reproduce, there is an increased incidence of marine pests suddenly appearing and causing havoc in our tanks. Many of these pests were probably in the tank before, but since we had difficulty keeping most animals alive for the long term, we most likely never noticed them. However, now that we can keep animals alive and thriving in our tanks for years, these pests are becoming more problematic. Fortunately, with this increased knowledge about pests, we are gaining an increased understanding of how to eliminate them. Even more encouraging is that in many cases we are able to eliminate these pests naturally.

Many pests arrive on the live rock or within the coral colonies themselves. One of the most frequently encountered of these pests is flatworms. These animals consume zooanxthellae as well as the coral's tissue. They are usually small and can only be detected by following the thin thread of dead tissue in the coral colony. The damage caused by the flatworms may not kill the colony directly, but may lead to a site for secondary infection. The best and easiest way to rid a tank of these pests is to introduce a mandarin fish which rapidly consume these pests as well other micro fauna in the tank.

Similar pests that may come in on live rock or that we may introduce ourselves are the nudibranchs. Most of these animals possess vibrant colors and interesting patterns so we can't help but consider them as worthy additions to our miniature reef community. In addition some of these animals possess the ability to mimic the coral upon which they feed. The nudibranch that feeds on Xenia and mimics its polyps is one that immediately comes to mind. However, their beautiful colors are only an indication of the poisonous nature. This poison, that is an integral part of the nudibranch's makeup, is derived from its food source of nematocysts. These nematocysts are the defense cells of many types of invertebrates including corals, anemones, jellyfish, etc.

Each species of nudibranch has a specific food source from which it derives these nematocysts. Therefore the addition of a single or small number of the same species of nudibranchs is not likely to decimate the entire invertebrate community. However, if these animals do find a coral to their liking it is very likely that the entire coral colony will be consumed if steps are not taken to remove the nudibranchs from the colony. Due to their poisonous nature these animals have few enemies and therefore will feed both during the day and at night. As a result they are relatively easy to see and attempt to remove.

There is also a new type of nudibranch that has recently become a pest because only now are we keeping some of its favorite food items. This nudibranch feeds exclusively on corals of the genus Montipora and more specifically Montipora capricornis. These relatively tiny nudibranchs are less that ΒΌ inch in size and look like the Berghia nudibranchs that have been used to eradicate Aiptasia anemones. These nudibranchs start feeding on the bottom of the capricornis colony, and once they have removed all of the tissue from the underside of the colony they will start to remove tissue from the upper more colorful regions. At this point the number of nudibranchs can be quite large.

Thanks to efforts by Leroy Headlee we have found that the only way to eradicate these pests is to soak the colony in freshwater for 30-45 seconds. This will cause the nudibranchs to burst apart and die. Do not soak for longer than necessary as this will kill the colony, and make sure that the water is matched for temperature and pH. The soaking then needs to be repeated at 10 days to kill any eggs that may hatch. This method has helped saved numerous capricornis colonies in my tank even when they were reduced to tiny colonies. I have however, found this freshwater treatment to be stressful to some colonies so before I try it I attempt to wash the nudibranchs off of the Montipora by removing it from the tank at night and then shaking it vigorously in a saltwater bath to dislodge the nudibranchs. This method can work even better if, after shaking in salt water the colony is inspected thoroughly with a flashlight and any nudibranchs that are left are removed with tweezers. Larger nudibranchs can be removed by siphoning them out of the coral head with a large diameter hose when they are not firmly attached to the substrate. When siphoning them out, siphon them to a separate container rather than into the sump to avoid any possibility of them poisoning the tank.

Unlike the nudibranchs which frequently show themselves due to their bright colors this next group of animals are extremely secretive and if they are seen it is generally as a streak of motion. For those of you with reef aquariums you know immediately that I am talking about mantis shrimp. While these animals are at least as interesting and colorful as the nudibranchs, they are much farther up on the scale of destructive animals that are very difficult to remove. These shrimps received their name because of their resemblance to a praying mantis. Like this insect, mantis shrimp possess lightning fast claws that they use for capturing food and defending themselves from enemies. Mantis shrimp possess keen vision from eyes that are placed on stalks which allow them to see around corners and from out of their burrows. In addition they are also sensitive to even the slightest vibration, so that if you are near the aquarium they can usually feel your presence and remain in their hole. Therefore rather than seeing them to know they are present, one needs to either listen for them or look for signs of their presence.

The very mechanism that makes them a formidable enemy, their powerful claws, also gives the mantis shrimp away. If some unknown source of clicking is occurring in your tank it is a good bet that a mantis shrimp is present. If the sound is a single loud click it probably is not a mantis shrimp, but most likely a pistol shrimp, which for the most part is harmless. If it is a mantis shrimp that is clicking, these are generally the less harmful of the shrimp as their diet consists primarily of mollusks. A better indicator of a mantis shrimp's presence is the disappearance of numerous small fish over time without a trace.

There are two types of mantis shrimp encountered: spearers and smashers. These names are descriptive of how the animal obtains its food. he spearer has exceedingly sharp claws that it moves very rapidly to spear or slice its prey or to defend itself. I have personally had this type of shrimp split my thumb open from top to first knuckle with a single flick of its claws. Therefore, handling them should be avoided even when trying to remove them. The smashers also move their claws in rapid fashion; however they move them in order to stun their prey. The movement is more ballistic in nature. These shrimp use their claws to crack open mollusks as well as to stun fish that get close enough.

In either case it is best to try and remove these pests as soon as possible. Unfortunately this is much more easily said than done. have found these animals to be one of the most cunning inhabitants of the reef. I have only been able to remove them by luck inspired ways. I either waited until I saw one enter a rock, then removed the rock or I trapped them in a fish trap in which I slowed the animal down by using bait wrapped in nylon stocking. There is no easy way to rid the tank of these pests, other than the previous methods as well as quarantine, which is discussed below.

The mantis shrimp is not the only crustacean that can cause damage within a reef tank. Several other crustaceans, especially crabs can cause at least as much damage. These harmful crabs should not be confused with the small little crabs of the genus Trapezius that inhabit many of the stony corals. The first of these are the Xenia crabs. These crabs only eat Xenia and consequently they are only infrequently encountered. However when they are present they very rapidly destroy a Xenia colony. These crabs match the color of the Xenia on which they feed and therefore they may not be detected until too late. These crabs generally are found in pairs, and the best time to find them is at night when they will appear as bumps on closed heads of Xenia. The best way I have found to remove them is to lift out the Xenia colony on which they are located and very gently push the crabs with tweezers or forceps off of the Xenia colony without damaging the colony.

Mike Paletta is the author of The New Marine Aquarium and Ultimate Marine Aquariums. He has been in the hobby for over 15 years and has written numerous articles for Aquarium Fish Magazine, Tropical Fish Hobbyist and Aquarium Frontiers.
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Article Details
Created on 4/13/2006.
Last Modified on 5/10/2006.
Last Modified by Administrator.
Article has been viewed 4126 times.
Rated 7 out of 10 based on 4 votes.
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