Coral and Invertebrate Quarantine Procedures

Decrease the chances of adding fish or coral diseases into your display tank.

For more than 20 years, my policy as the Toledo Zoo’s aquarium curator has been to quarantine all newly arrived fish for a minimum of six weeks. Treating the fish with a wide arsenal of prophylactic medications during this process has proven effective, with very few losses of post-quarantine fish to marine ich (Cryptocaryon irritans) or velvet (Amyloodinium ocellatum) during that entire period.

Since we consistently started using praziquantel about 12 years ago, there have also been very few losses of post-quarantine fish due to trematode (fluke) infestations. Certainly fish still die, sometimes from undetermined causes, but for the most part, these major fish disease scourges have been brought under control by using this quarantine protocol.

Quarantine Protocol
The quarantine procedure for invertebrates that I established during this same time had a different objective: primarily to avoid the transmission of fish diseases carried in on the invertebrates (and the water they were shipped in) to existing fish populations. This was done by simply isolating new invertebrates for at least seven days in a system not housing any fish. Invertebrate-to-invertebrate disease transmission was not a major concern because that problem seemed fairly rare. Recently, I’ve changed my opinion because a series of coral shipments brought a number of coral diseases and pests into our previously stable invertebrate systems.

Stony corals are listed as CITES Appendix II organisms and require proper import and export permits in order to travel between countries. In some cases, corals arrive in the United States without proper permits. These are confiscated by the United States Fish and Wildlife Service. The USFWS in turn may elect to send these corals to public aquariums for safekeeping. The aquarium that I curate has always cooperated with the USFWS and accepted shipments of these corals. However, it became apparent that the same exporters that didn’t bother to get the required permits also tended to be lax in their care of corals. We found that our off-exhibit coral propagation systems (where we placed these corals) were becoming infested with a variety of coral diseases and pests. In response, we re-examined our own invertebrate quarantine protocols and developed some techniques applicable to home aquarists, as well.

Invertebrates as Vectors for Fish Diseases
One reason to properly quarantine newly acquired invertebrates is to reduce the possibility that their introduction may carry fish disease organisms into an aquarium. It is well-known that transferring small amounts of water from one aquarium to another can carry disease organisms along with that water into the new tank. Pet dealers typically use strong disinfecting solutions (formalin or bleach) to reduce the chance of this happening when moving wet fish nets from one tank to another. Since there is a risk that fish diseases will adhere to the small volume of water on a wet fish net, it stands to reason that these same diseases can be transferred in any water moved from tank to tank, including water attached to invertebrates (or live rock).

With invertebrates, however, the use of strong disinfectants is of course not possible. Keep the invertebrate (or live rock) isolated from fish for longer than the parasites can survive without a fish host. This way the transfer can be made without introducing diseases to the fish. The problem is that this “clearing period” for fish parasites is not known with much certainty. Some anecdotal information indicates that saltwater ich (C. irritans) can remain infective for up to 30 days without a host. Neobenedenia melleni (an egglaying trematode) produces sticky eggs that may remain viable and potentially infective for more than 14 days. If the invertebrate cannot be isolated from the general fish population for at least a month (the best-case scenario), other steps might help. Aquarists can rinse the invertebrate with freshly mixed, sterile seawater to reduce the potential for disease introduction by physically washing away infective organisms.

Proper acclimation

Invertebrate Quarantine Acclimation
The first stage of any quarantine process is the acclimation of the animal to the quarantine tank. The basic process is to change the water parameters from the water the animal was shipped in to that of the destination aquarium. This change must be done at a slow enough rate to not cause undue stress to the animal but not so long as to have it cause stress. Avoid the temptation to “reduce stress” by greatly stretching out the acclimation process beyond the recommended timeframe — taking too long to acclimate an animal is just as bad as not acclimating long enough. This is a difficult concept because it seems counterintuitive: An animal undergoing acute stress from transport is going to have increased stress the longer it stays outside the proper parameters. The crux of this issue is that some aquarists think that if a one-hour acclimation time is good, then a 10-hour acclimation time must be 10 times as good — but this is definitely not the case.
There are a variety of methods to acclimate invertebrates, and different types of invertebrates have different requirements. Many invertebrates, such as anemones, corals and snails, are not affected by changes in water parameters — as long as the starting and ending parameters are within appropriate limits for that species. Octopuses, shrimp, sea stars and sea urchins, on the other hand, are very sensitive to rapid changes in pH or salinity. These animals must always be acclimated gradually, as you would a fish.
It is usually best to follow your dealer’s advice for acclimation. The following are three acclimation techniques:

  1. No acclimation. Any organism that is shipped damp and not in water doesn’t need to be acclimated (such as live rock and damp-packed corals). Gently rinse the rock or coral off with some tank water (properly disposing of the rinse water) and place it in the aquarium.
  2. Acclimation in the bag. If you have not been given directions for acclimating the specimen and the animals have been in their shipping bags for less than 15 hours, use the following basic method.
    Step 1: Float the bag in the aquarium with the lights off for 15 minutes. Add aeration, if needed, and add 25 percent tank water to the bag. Wait five minutes.
    Step 2: Remove the water from the bag (properly dispose of this water) to reduce it back to its starting volume, and add 50 percent tank water to the bag. Wait five minutes.
    Step 3: Remove water from the bag to again reduce to its starting volume and add 100 percent tank water. Wait five minutes.
    Step 4: Carefully release the specimen into the quarantine tank and dispose of the remaining water.
  3. Minimize ammonia and then acclimate. Shipments taking longer than 15 hours require special acclimation techniques in order to minimize ammonia levels. The basic technique involves preparing water that is identical to the bag’s water in temperature, pH and specific gravity. Then move the animal directly into that prepared water so that there is no ammonia. Then at this point, it can be acclimated in the bag (see the “acclimation in the bag” technique described earlier).

Acute Problem Quarantine
Think of this quarantine method as being a medical triage for new arrivals. This technique is useful in shipments of invertebrates that have been delayed during transport or otherwise mishandled, or if you suspect that the source aquarium may have serious problems.
After acclimation, the coral or invertebrate is isolated in a stable, lower-light environment to assess it for immediate health problems. The main concern is to avoid adding a coral that is about to “crash” to a system with stable animals. This crash can release huge numbers of bacteria and protozoa that feed on the dying coral, and these can overwhelm and infect stable corals. This can also be a useful method for handling invertebrates, such as sea cucumbers, that sometimes release toxins after being stressed during shipment.

The basic procedure is to prepare a clean plastic container or tank, provide it with relatively lower light levels (slightly lower light than the animal was accustomed to), an operating biofilter (perhaps a seasoned sponge filter) and the ability to maintain a proper temperature. Because of the small water volume, ultraviolet sterilization may also prove helpful in reducing bacteria loads in the system. Hold the invertebrate for four to seven days, monitoring and maintaining water quality at all times. If no acute problems develop, either add it directly to a system or follow the chronic problem protocol below.

Chronic Problem Quarantine
More commonly, corals, live rock and some other sessile invertebrates have the potential to bring “hitchhikers” with them when they are transferred to a new aquarium. By far, the number one scourge is an infestation of glass anemones (Aiptasia spp.). Even one tiny anemone adhering to the base of a new coral can bring a plague to your display aquarium in a matter of months. Other pests include various mantis shrimp and crabs that may arrive hiding inside live rock. Red bugs that attack Acropora corals, nudibranchs that feed on Montipora corals and flatworms that eat Acropora corals are all problems frequently introduced with new animals.

Some argue that you can never completely eliminate the chance for introducing pests, but many of the people who believe this do not institute any sort of quarantine for their new invertebrates. Quarantine can and does help reduce the chance of pest introduction into your main aquarium. The basic process is to have a small but completely furnished reef aquarium established where invertebrates (primarily corals) are held in a pristine environment for at least eight weeks. This is also a perfect time to perform any light acclimation that your new corals may need.
After acclimation to the quarantine tank, place each new coral colony on a contrasting (different color from the tank’s substrate) smooth surface so that pests can more easily be seen. Egg crate, while good for anchoring coral frags, is also a good place for coral pests to hide. A smooth surface works well if the coral has a base that will allow it to sit upright.

The colonies must be inspected for pests every few days and treated for problems accordingly. This method takes time and effort, and it is most economical when done with a whole shipment of corals at the same time (most likely, retailers and other aquarium professionals would find this useful). This process is good for weeding out serious pest issues that may be transferred on corals.

There are three treatment types for invertebrate problems: chemotherapy (dips and drugs added to the water), biological controls (adding other animals to control pests) and environmental maintenance (changing the aquarium’s environment to favor one animal over another).

This is a difficult treatment method to use with invertebrates, as many of the pests you are trying to control have the same or even less sensitivity to a given drug than the corals do. Target applications can be used, such as topical chemical applications to control Aiptasia anemones. In other cases, dips have become popular. Finally, there are systemic drugs, such as praziquantel, that are toxic to only certain groups of invertebrates.

Further Reading
Hemdal, J.F. 2006. Advanced Marine Aquarium Techniques. 352 pp. TFH Publications, Neptune City, New Jersey.
Hemdal, J.F. 1992. “The Use of Calcium Hydroxide to Control Aiptasia Anemones.” Freshwater and Marine Aquarium magazine, 15(4):122. RC Modeler Corp., Sierra Madre, California.


For active quarantine systems, coral dips show the most promise. However, there are a variety of dips available; some work for certain problems, and others seem to show no real benefit. Use your dealer’s advice and the advice of people who have successfully used a given dip method. Avoid using any product that doesn’t list its ingredients on the label.

Biological Control Methods
These include using a copperband butterflyfish and perhaps Berghia nudibranchs to control Aiptasia anemones, a sixline wrasse to control flatworms, and snails to control pest algae. These methods are best applied in instances where a pest has entered your main reef aquarium, as they take time to work and rarely, if ever, completely eliminate a problem.

Environmental Control Methods
Many coral protozoal and bacterial diseases are ubiquitous; they are found in most aquariums but only cause real problems when the corals are weakened by environmental problems. Improving the environment for the corals may allow them to become strong enough to fight off the disease and pests. In other cases, changing the environment by directing water flow can help mechanically brush off pests such as flatworms. Certainly, reducing dissolved wastes, such as nitrate and phosphorus, can improve a coral’s environment and help it fend off disease and pests.

In some cases, there simply is no truly effective treatment for a given problem (such as brown jelly disease). Having these devastating problems show up in a quarantine tank is much preferable to seeing them in your main reef tank. In these cases, you may try to frag it and remove the affected tissues with the hopes that the healthy frags will regrow. Keep the new frags in quarantine until there is no chance that disease can be added into a healthy display tank.

Quarantine protocols for invertebrates serve two basic functions: to help protect your existing animals from newly introduced diseases and to allow a place to more effectively treat the new animals should they exhibit a problem. Any quarantine protocol is a balance of cost (in money, time and resources) and efficacy (how successful the procedure is at preventing the loss of preexisting animals). Using no quarantine at all has the lowest “cost” but also has no benefit. By contrast a six-month quarantine would eliminate almost all chance of disease introduction but would require a larger amount of resources. Most home aquarists will opt for some plan between these two extremes. AFI

Jay Hemdal has worked in public aquariums for two decades and is the Curator of Fishes and Invertebrates at the Toledo Zoo. He wrote the books Aquarium Careers and Aquarium Fish Breeding, and has written more than 100 magazine articles on aquarium-related topics.


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Fish · Saltwater Fish