SaltwaterSense

Symbiosis in the Saltwater Aquarium

One of my favorite aspects of keeping a marine aquarium is the opportunity to observe symbiotic relationships up close. The reef is a highly competitive environment, and many reef animals develop relationships with other animals to increase their chances of survival. Some of these relationships benefit both animals, while others only benefit one of the two. Setting up the proper conditions to observe some of these relationships in the aquarium is, in my opinion, well worth the effort, and here are a few symbiotic relationships most aquarists with a stable, mature system can attempt to replicate in his or her system.

Clownfish-Anemone

The symbiotic relationship shared between a clownfish and an anemone is one of the most well-known and oft replicated symbiotic relationships within reach of most aquarist. To insure success, the aquarium must be able to support the anemone, which is, in general terms, a more difficult-to-keep animal than the fish. Most anemones require a stable tank that is at least six months old, and some anemones have even more specific requirements—so be sure to do your research. The bubble tip anemone (or BTA, Entacmaea quadricolor) is a good anemone with which to start, and many clownfishes will readily form a relationship with it. Having said this, not all clownfishes will host in an anemone, even if one is present in the aquarium.

Commensal Crab-Coral or Anemone

There are many crabs that will readily form a relationship with various invertebrates including both anemones and many coral species, especially from the genus Euphyllia (e.g., torch coral). The anemone or porcelain crab, for example, (Neopetrolisthes spp.) is a small, non-aggressive crab that will readily live within the tentacles of an anemone or coral species. Again, the conditions in the aquarium must be able to support the anemone or coral, and this usually means the tank will be mature (at least six months old) and stable. In addition, the salinity should be kept at near ocean levels, as most inverts will not do well in hypo-saline conditions.

Commensal Shrimp-Coral or Anemone

Like the commensal crab that lives in association with an anemone or coral, commensal shrimp will readily form a relationship with both coral species (especially from the genus Euphyllia) and anemones. One of the best commensal shrimps to keep is the so-called sexy shrimp (Thor amboinensis). This is a small shrimp with gaudy colors and a unique movement that resembles a somewhat lurid dance (hence the name). While they will host in anemones, the sexy shrimp does particularly well when living in close association with Euphyllia spp.  

Goby-Shrimp

The relationship formed between a goby and a shrimp is wonderful to watch. While it is possible to observe this relationship in a large reef tank, the pairing of a goby with an appropriate shrimp can easily be the centerpiece of a nano tank. In general, the goby will dig a burrow, which it will then share with the shrimp. When the shrimp ventures out of the burrow, it relies on the goby to make sure the coast is clear. Consider gobies from the genera Amblyeleotris and Stonogobiops and pair them with shrimp from the genera Alpheus and Synalpheus.

Conclusion

There are many other symbiotic relationships which the aquarists can host in his or her aquarium, but these are some of my favorite. Remember to check compatibility charts and to do your research with any species BEFORE you acquire it. In the case of commensal shrimp and crabs, it is often wise to purchase several of these animals if you are planning to add them to a community reef tank, as you may lose one or more from natural predation. To increase your chances of success, add the animals at night directly adjacent to the intended host.

Angelfishes from the Genus Genicanthus are Fantastic Reef Aquarium Fishes

Many saltwater aquarists are inspired to take up the hobby after observing the beauty of an angelfish or the stunning, almost extraterrestrial, growth forms of coral species. Or both. Unfortunately, many angelfishes are incompatible with a reef tank, so keeping the two together is not a good idea. There is, however, one genus of angelfishes that is indeed quite suitable for the reef tank, and it is this genus I want to discuss today.  

Angelfishes from the genus Genicanthus are commonly called swallowtail or lyretail angelfish because of their distinctive tailfins, and they make great reef aquarium angelfishes. If you look closely, you will see that the species in this genus have small mouths. This is because these fishes are planktavores that feed primarily on plankton in the water column—not coral!

The upside to keeping angelfishes from the genus Genicanthus does not stop with their feeding habits, however. These fishes are, generally-speaking, long-lived and peaceful animals that make great community reef fishes, and their small size means they don’t require the massive amount of space that some of the other angelfishes require. Do be cautious when adding a Genicanthus angelfish to a reef tank housing smaller planktavores (especially certain gobies and wrasses), as the smaller fishes may be harassed as they compete for the same foodstuff.

Another great attribute to angelfishes from the genus Genicanthus is that they may be kept successfully in small groups. The aquarist may plan to keep one male with one or more females. Theses angelfishes, are known for their dramatic sexual dimorphism and dichromatism (in short, males and females are different in shape and color), which makes keeping a pair or small harem both behaviorally interesting and aesthetically appealing.

Members of the genus are generally parasite and disease resistant, but they should, like all fishes, be properly acclimated and quarantined.

Of the Genicanthus angelfishes most commonly available to the tropical marine aquarist, the bellus angelfish (G. bellus), the Watanabei’s angelfish (G. Watanabei), the Lamarck’s angelfish (G. Lamarck), and the swallowtail angelfish (G. melanospilus) are some of my personal favorites. If you are looking for the ideal reef-compatible angelfish, look no further than the angelfishes from the genus Genicanthus.

Mixing Dwarf Angelfish Species in a Saltwater Aquarium

Centropyge angelfishes, commonly referred to as dwarf angelfishes by hobbyists, are known for their beauty AND their territorial behavior. The former is often the reason why aquarists choose to add one to their aquarium, and the latter is why many aquarists often add only one. While this may be a prudent course of action, there is, however, no reason that the thoughtful aquarist can’t keep multiple species of angelfishes from the genus Centropyge in the same aquarium.

Let’s keep in mind the big picture concepts. The reef is a highly competitive environment, and establishing and maintaining territory on the reef can be cutthroat. For a small fish, like many dwarf angelfish species, this can mean that the fish has evolved into a scrappy little tyrant. It’s not that the fish is “mean,” rather it is that the animal is simply genetically programmed to survive the competitive environment of the reef, and this behavior will carry over into the aquarium.

What does this territorial behavior look like in the aquarium? Chances are that a dwarf angelfish will be most aggressive with any fish that poses a threat. A threat may be perceived as any fish that naturally occupies the same niche on the reef, utilizes the same resources, (e.g., food) and may compete for reproductive mates. One can easily extrapolate from this that dwarf angelfishes of roughly the same size, shape and color, that exhibit the same feeding behavior, will be least likely to get along.

So let’s apply these concepts to stocking procedures in your aquarium. Because the dwarf angelfish is often scrappy and territorial, it should be added last (or close to last) in your stocking order. This gives all the other fishes in your aquarium a change to become established first. Unless the aquarium is very large, two dwarf angelfishes of the same species should usually be avoided by all but the most experienced aquarists. Likewise, angelfish species that are very similar in shape, size and color should be avoided.   

If you are going to add two dwarf angelfishes of different species, add them at the same time if at all possible. Keep the lights low during acclimation, and be sure the system is “mature” (read: plenty of algae on the live rock). Alternatively, add two pieces of live rock that are covered in algae at opposite ends of the aquarium. If you can’t add the two fishes at the same time, make sure that the second dwarf angelfish added to the system is the larger dwarf angelfish. For example, I would add a cherub dwarf angelfish (C. argi) to my system and then, several weeks later, consider adding a flameback angel (C. aurantonotus) or a flame angelfish (C. loriculus).

In general, the proper environment makes a difference when trying to house multiple Centropyge angelfishes of different species in the same aquarium. Basically this means the larger the aquarium the better, and the more live rock in the aquarium the better. Be sure the aquarium is not too “clean”, as providing algal growth on the live rock at which the fish may pick will occupy its time.

A large aquarium with loads of live rock and sufficient algae growth should be able to support two or more dwarf angelfishes of different species with no problem, if you follow the advice given here.

Using Reef Herbivores to Control Algae in the Saltwater Aquarium

I saw Eric Borneman give an interesting talk on reef herbivores last week at MAX, and it just so happens I have a feature article on the same topic in the current issue of Tropical Reef Hobbyist Magaine (p. 94 of the May issue). Understanding reef herbivory is central, in my opinion, to being a successful reef hobbyist. It also sets the reader up for being on the front line of one of the more important reef conservation fronts of our time.

Cows and Fertilizer

Eric’s talk was called “Cows and Fertilizer: a Novel Way to Understand the Control of Algae in Reef Aquariums.” It made the analogy between terrestrial herbivory, which most people readily understand, and reef herbivory, which, for many, remains somewhat of a mystery. Basically, when you think of algae on a reef—either a natural reef or one in an aquarium—you can think about it as being caused primarily by excessive nutrients  or primarily by lack of appropriate herbivores. Aquarists tend to think in terms of the former when they have an algae control issue, but both Eric’s talk and my article in TFH encourage the aquarist to think more about the latter.

Herbivores in the Saltwater Aquarium

Understanding what herbivores eat what on the reef can have a dramatic impact on the control of algae in a marine aquarium. Understanding that each herbivore occupies a critical function on the reef in terms of the algae it targets and where it targets that algae will help the aquarist maintain a “clean reef” without needing to rely heavily on overskimming and other mechanical and chemical nutrient export. Mind you, I‘m not suggesting not to use a protein skimmer or run nutrient absorbing media in your aquarium, but I am suggesting that you give some real thought to exactly how you use your livestock to assist in the fight against unsightly nuisance algae.

Rabbitfish (not Parrotfish!) for Control of Nuisance Algae

In my article in TFH, I look primarily at algae grazing fishes that have been shown to be excellent herbivores on the reef (e.g., the rabbitfishes), but I also point out that it is a combination of algae-grazing mollusks and herbivorous fishes that generally proves most effective. The take-home point is that herbivory is at least as important as nutrient control on natural reefs AND in your aquarium. Understanding the ecological niches of fish, both on the reef and in the aquarium, can help elucidate why things like algae outbreaks happen, and how to fix them when they go wrong, while keeping in mind that some very important reef herbivores are poorly suited to most marine aquarium sitautions (e.g., parrotfishes). 

Applying Data about Algae-Dominated Reefs to the Marine Aquarium

As is often my approach when dealing with my own aquarium, my TFH article looks to what goes on in the wild as observed by marine researchers, and tries to apply that knowledge to successfully maintaining a marine aquarium. As Eric’s talk pointed out, however, the marine aquarium is VERY different from the actual reef in terms of how the entire system functions. Nonetheless, keeping the broad concepts in mind regarding both herbivory and nutrients can improve one’s husbandry dramatically. Using both nutrient control and herbivorous fishes and invertebrates can help the aquarist finally win the war against nuisance marine algae, while at the same time developing a better understanding of why natural reefs are increasingly becoming algae-dominated and why this is something about which we all should be concerned.

Success with a Mixed Hard and Soft Coral Aquarium

I am an addict. I know. I admit it. That’s why I recently started not one, but two new saltwater tanks.

Admittedly, having multiple tropical saltwater aquaria gives me the ability to create different biotopes and avoid some common compatibility issues, but what if you only have one tank and you want to keep species that may potentially be harmful to one another? In most cases, best practices says don’t do it unless you are very experienced, have a massive system or are prepared to offer round-the-clock husbandry during the introduction and acclimation period. Mixing hard and soft corals may well be the best example of an exception to the rule, and that’s what I want to talk about today.

Let’s start out by discussing the compatibility issue itself. Imagine this relatively common scenario: A new saltwater hobbyist starts his or her first tank. He or she decides to go reef and are advised to begin with so-called “starter corals” such as leather or soft corals. After half a year of success with the soft corals, the aquarist starts thinking he or she might be ready to have a go at hard corals, but then someone tells them you can’t mix hard and soft corals in marine aquarium. Is this true?

Yes and no. First the facts:

• Most soft corals are easier to keep than hard corals.

• Many of the most popular soft corals are also some of the most toxic animals commonly kept in the hobby.

• Some of the more prized hard corals (especially those referred to as SPS corals) are particularly susceptible to the chemical warfare of which many soft corals are capable.

In other words, adding a hard coral to a soft coral-dominated tank can mean the demise of the hard coral as the soft corals in the tank—even if not directly proximal to the hard coral—release their toxins and mucous webs in an effort to repel the invader.

Whoa! That really happens? Yep.

While many soft corals are great beginner corals because they tolerate varied conditions, are less expensive and happen to be quite beautiful, they also are fully capable of allelopathy (chemical warfare) that can wipe out hard corals. Some soft corals can even sense a competing hard coral, even if it is several feet away, and, in the closed system of an aquarium, the resulting allelopathy can be fatal to the new addition.

But wait! I started this entry by saying that mixing hard and soft corals may well be the best example of an exception to the rule of avoiding known compatibility issues as a matter of course. It’s true. By being smart, showing restraint and slightly altering his or her husbandry and maintenance protocols, even the beginning aquarist can have success with a mixed tank. Here’s how:

• Research ever species thoroughly before purchase, and go slow when starting out.

• To begin, make sure each soft coral specimen has up to eight inches of buffer around it.

• Run robust filtration so that toxins are quickly diluted and then removed from the system.

• Run a reverse flow substrate reactor with carbon as a normal part of chemical filtration.

• Observe! Observe! Observe! And then adapt if necessary.

By following these simple points, even the beginning tropical saltwater aquarist can have success with a mixed tank containing both hard and soft corals.

Maybe I should start another tank and make it a mixed tank!

Captive-Bred Marine Aquarium Fishes--The Right Choice?

It seems it is really hard to sell a captive-bred animal in today’s marine aquarium industry, and I’m not entirely sure what that is all about.

Sure, a tank-raised fish is usually more expensive, but it is also generally a hardier animal. In addition to captive-bred fishes being better suited for aquarium life than wild-caught fishes, over the past few months there’s been a slew of press against purchasing certain wild-caught animals like the Banggai cardinalfish. In the case of the Banggai cardinalfish, concerns over stable wild populations have led the marine aquarium hobby press to call for a self-imposed ban on wild-caught specimens of this spectacular fish. And yet a sea change has not occurred, and hobbyists are still buying wild-caught fishes. Why is this?

In the case of the Banggai cardinalfish, it has everything to do with the fact that despite the press’ full-court press, nobody—and I mean NOBODY—is supplying tank-raised Banggai cardinalfish on a commercial level to the industry at present. I conducted my very own, unscientific survey a couple weeks ago by travelling to no less than seven local fish stores in the Los Angeles area. While many of these stores had Banggai cardinalfishes, nobody had tank-raised ones or even knew where they could get them. When I asked whether or not hobbyists had been requesting captive bred Banggais, the response was a categorical “no.”

I understand it’s hard for the hobbyist to buy something that is not available, but, by the same token, without the demand, where is the incentive for people to start commercially breeding Banggai cardinalfishes? Or to place the responsibility more firmly with the hobbyist, why are responsible aquarists not demanding captive-bred fish? When faced with the decision between buying a tank-raised fish and a wild-caught fish, why are aquarists not choosing the tank-raised animal more? Either aquarists 1) don’t buy the line that tank-raised fishes are, more often than not, a more suitable choice for the aquarium, 2) don’t believe that wild populations of some fishes are in a dangerous state of decline, or 3) aren’t willing to pay more money for a tank-raised fish.

While I hate to say this, I do believe it comes down to lack of education and money. Why do I say this? Because I don’t want to say that the marine aquarist doesn’t care. I believe that most marine aquarists are good people who have a profound appreciation for the ocean and the animals that live in it. Most aquarists I know want to do the right thing, even if that means paying more for a captive-bred animal. This is why I will be dedicating several blog posts here at SaltwaterSense to the topic of captive-bred marine fishes throughout 2009.

I will not advocate (as some recently have) that the industry should, in the future, depend entirely on captive-bred species. This is neither realistic, nor is it in the best interest of impoverished island nations where the marine aquarium industry provides a valuable source of income to local communities. I do believe we need to ramp-up commercial breeding programs for many popular marine aquarium fishes like dwarf angelfishes, certain tangs and, of course, Banggai cardinafishes, but I also believe we need to educate hobbyists on where upwards of 95% of marine aquarium fishes are collected. We need to begin initiatives to help local fishermen develop sustainable fisheries that conserve the ecosystem and supply a robust and sustainable marine aquarium industry. And of course we need to educate the hobbyist about why, in some cases, demanding and buying the more expensive tank-raised species is the right thing to do.

Stocking Your Saltwater Tank Like the Dubai Aquarium...NOT

You may or may not have heard about the shark issues facing the Dubai Aquarium. In what is being billed as the world’s single largest captive school of sharks (over 400 sharks and rays), sharks are killing sharks at an alarming rate. Some reports have suggested that the Dubai Aquarium’s sand tiger sharks (Carcharias taurus), of which there are at least 45 individuals, have killed up to 10 percent of the entire population of sharks housed behind the world’s largest viewing panel. As aquarists, we might look at this as a stocking issue of unprecedented proportions.

A Significant Error?

Like the Dubai Aquarium, marine aquarists commonly keep multiple species together in their aquaria. The aquarium-going public is used to seeing tanks that house an impressive array of species that live together in what appears to be a relatively peaceful environment. The Dubai Aquarium, which is set to open at the end of this month (October 2008), will house more than 33,000 aquatic animals representing 85 marine species, but—given the sand tiger shark’s behavior—it seems a significant error may have been made in either the Aquarium’s stocking plan or in their approach to husbandry.

As marine aquarists know, a great deal of forethought must go in to planning any marine aquarium be it a fish only system, an invertebrate aquarium or a full-blown reef tank. Of course there are the equipment considerations, but there is also the all-important stocking plan. A stocking plan is simply the roadmap outlining what animals will be housed in the aquarium and the order in which those animals will be added to the aquarium. While there are many ways to go about creating a stocking plan, I personally prefer the biotope approach.

A Biotope Approach

The biotope approach to stocking an aquarium is, in my opinion, an excellent approach. While not the only approach, it lessens the chances for aggression, provides the opportunity for creating some stunning symbiotic relationships and allows the aquarist to better understand wild ecosystems. The word biotope comes to us from the Greek and literally translates as “life place.”

A biotope approach to stocking your aquarium begins, usually, with a single species that defines the biotope being replicated. This species is generally an animal or plant that spends its whole life within a very small area. In most cases, we are speaking of sessile animals (ones that do not move about very much if at all). In the wild, a coral, anemone, or even a marine plant will attract a host of other organisms that will develop a relationship with the biotope species. Replicating these relationships in the aquarium is a good approach to planning your next tank.

Increasingly Larger Animals Round Out the Aquarium

Working up from the biotope species, the aquarists may choose increasingly larger organisms that are less associated with the biotope species, but which are also native to the biotope being replicated. A commensal invertebrate such as a coral or anemone crab may, for example, spend its entire life within the branches, polyps or tentacles of the biotope species. On the other hand, a reef-associated fish may move through many biotopes in the course of its day.

A nice byproduct of the biotope approach to stocking your tank is that, in addition to coming up with a stocking list, you also develop an appropriate stocking order. One way to think of the biotope approach is that a full tank picture of your fully stocked aquarium may well look like a photograph taken on the reef. Does this mean that every photograph taken on the reef can be the roadmap to your stocking plan? Definitely not.

Research Still Needed to Avoid Problems

As most aquarists know, although a large shoal of yellow tangs may be a common site on some natural reefs, more than one adult yellow tang in a saltwater aquarium (unless it is very large) generally means trouble. As such, even with the biotope approach, it is important to consult compatibility charts and research each individual species before finalizing the stocking list.

Would a biotope approach to stocking have helped the Dubai Aquarium avoid the shark killings they have experienced to date? It’s hard to say given the unprecedented nature of the intended display. It is clear, however, that individuals associated with the Dubai Aquarium had some very specific ideas in mind regarding what would draw the crowds. After all, the Dubai Aquarium is, at least on some level, a means to an ends, and that ends is to bring more people to the world’s largest retail real estate project—the Dubai Mall.

The Dubai Mall's own literature advertises the shark exhibit as “an adrenaline-fueled visual experience.” I would hazard to guess that a biotope approach may have produced a somewhat different result.