The Use, Overuse, and Abuse of Biological Controls

There was an old lady who swallowed a fly. I don’t know why she swallowed the fly. Perhaps she’ll die. There was an old lady who swallowed a spider that wiggled and giggled and tickled inside her. She swallowed the spider to catch the fly. I don’t know why she swallowed the fly. Perhaps she’ll die. There was an old lady who swallowed a bird. How absurd! She swallowed a bird. She swallowed the bird to catch the spider…

For those of you with young children, I am sure this nursery rhyme is familiar. Or perhaps it has sparked a memory of your own from when you were young. I bring up this little story to illustrate a point about the many instances where biological controls are used inappropriately or overused.

First off, I guess I should discuss just what a biological control is. It is when you utilize a live organism to control or eradicate another organism that is considered to be a pest or predator. Examples in aquarium keeping are very common. Snails, hermit crabs, urchins, Surgeonfish, and some Blennies are used everyday to control diatoms, algae, and cyanobacteria. People attempt to use Peppermint Shrimp, Berghia nudibranches, or Copperbanded Butterflyfish to rid their tanks of aiptasia anemones. Dragonets and certain wrasses are sometimes employed to control flatworms with varying levels of success. The list goes on and on. But, do any of these animals really do what has been claimed; namely that they can eradicate a nuisance for the aquarist without any work on their part?

Let us take for example the newbie aquarist who has just purchased his first saltwater setup. He has just completed the installation of his 30 gallon slice of the ocean. He then releases his first acquisitions, two Ocellaris clownfish and promptly named them Marlin and Nemo. Things are going pretty well for the first few weeks. He was lucky enough to have purchased fully cured liverock from the local fish store and since it was not a long drive home, he dodged the bullet regarding cycling.

Like most beginners, he has a tendency to overfeed. When he details the fuzzy globs sitting at the bottom of his tank, the shop owner tells him that he is giving them too much food. That he needs to cut back, but that he can buy a starfish to clean up the bottom. He takes this really neat looking green brittle seastar (Ophiarachna species) home and proudly shows his wife this strange new addition. Everything is cruising along swimmingly. The starfish has picked up all the excess food and the captive raised Clownfishes don’t venture far from the top of the display, the area where the food is dropped, so they have avoided the starfish thus far. The problem has been solved, but the invisible nutrients from the uneaten food remain in the system.

While some people are afraid of these because they have heard certain reef keeping gurus accuse them of eating corals, the majority of Asterina seastars one finds in aquaria are tan colored, found on the glass or sand, and eat diatoms. I would however remove any that are pink, purple, or found consistently on and around corals as these could be predatory.

After a few weeks though, he has noticed some nasty looking brown scum growing on the glass, sand, and rockwork. He runs to the fish place and is informed he has what are called diatoms. They are normal, but that he can buy some Astraea snails to help control their growth. He agrees. The new aquarist is given the rule of thumb that an aquarium requires 1 clean up crew animal for every gallon of water. Since he has a 30 gallon tank, he is told he will need 30 snails to get rid of this nuisance algae. Bag’em up, he replies. He takes these home, does a careful drip acclimation like he was told, and these snails promptly go to work. He is amazed at how quickly the diatoms disappear and he is very pleased with most of these hard-working snails. He uses the word ‘most’ because some seem to be very old and in need of Medic Alert bracelets since they are constantly falling and can’t get up. But all in all, he is very pleased with their cleaning duties. Although, the invisible nutrients are still in the water.

About now, these invisible nutrients are beginning to fuel some hair algae. This necessitates another trip to the pet store where he buys 10 hermit crabs, 5 blue legs and 5 scarlet reef hermits, plus the Dory fish that he has been keeping an eye on for the past week. This combination is supposed to mow down his hair algae in no time. And, it does. He is truly amazed at his luck. All his life he has heard horror stories of attempts to keep a marine aquarium, but in his mind, he has done exceptionally well. This is in no small part to the excellent advice he has received from his local fish store. Every time he has any trouble, they seem to know exactly what he needs to maintain the delicate balance in his aquarium.

About a week later, he notices something is awry with this Blue Tang, Dory. She quit eating, has been hiding more, seems to be panting, and looks like some of the sand is stuck to her body. So, he makes the trip back to the pet shop. This time the owner is not there, but a competent sounding young lady helps him. She says his fish has Marine Ich and needs a couple of Cleaner Shrimp, like Jacques in the movie Finding Nemo. This makes sense to him. He has had good experience with the other biological controls and the Finding Nemo reference seals the deal. He takes a pair of shrimp home, does the same drip acclimation technique he learned with the snails, and sends them off to do their work. They immediately setup cleaning stations and appear to be doing some good because he watches the Tang approach them, the shrimp climb all over the Tang, and after a few days the spots disappeared. But alas, they reappeared a few days later and this time the Clownfish are covered, too.

Things start to go downhill quickly for Mr. New Aquarist at this point. He wakes up one morning to find the Green Brittle Starfish happily munching away on poor Dory. And, it is not long before the Clownfish are found to have perished. At the same time, the hair algae is growing like mad now and there is also this nasty slime algae which he is later told is cyanobacteria. The whole tank looks awful and he is cursing the hermit crabs and cleaner shrimp for not keeping the place looking better. But, the shrimp seem more inclined to eat the fish food then to clean house. And, he swears the hermit crabs have gone psychotic because he believes they are killing snails even though he has not been able to catch one of these serial killers in the act. By now he is totally frustrated. The kids cried a great deal when they had to send Dory, Marlin, and Nemo back to the sea where they came from with a flush. And, his at one time beautiful ocean display looks more like a tiny cesspool. A few weeks go by and he is happy to sell the whole thing for ten cents on the dollar in an ad in the local newspaper.

I use this little piece of fiction to illustrate a larger point. Take a step back and try to determine the underlying causes of any tank troubles you experience. Far too often, we have a reflex to run to the store to get a solution to the perceived problem. In many of these instances, the actual cause is overlooked or ignored while the symptoms are treated. That is not a long-term recipe for success in this hobby. I can categorically say that any and all nuisance algae problems, whether it is cyanobacteria, hair algae, dinoflagellates, Bryopsis, bubble algae, etc., has the same root cause, excess nutrients. But, that is good because that means the cure is the same for any of these plagues. All one needs to starve any outbreak back under control is the following:
– Aggressive and efficient protein skimming
– Regular water changes of the appropriate volume and frequency
– Purified source of water (RO, RO/DI, DI-only, etc.)
– High quality salt mix devoid of nitrates and phosphates
– Consistent and appropriate levels for pH, calcium, and alkalinity to encourage coralline algae
– Careful feeding and dosing (don’t dose what you can’t test for and only feed what your inhabitants can consume in a minute or two)
– Refugium with macroalgae harvesting to compete against the nuisance outbreak
– And, possibly the use of activated carbon and/or other chemical filtration media

That is not to say that I am completely against using biological controls. There are several that I think are absolutely fabulous. Asterina seastars, mini brittle stars, strombus, stomatella, and cerith snails are some of my favorites. I prefer these because they all are known to reproduce easily and have offspring that survive to adulthood in captivity. All one needs to do is introduce a small group of any of these creatures and they tend to reproduce to a level that controls the particular type of algae they prefer to consume.

While algae blennies are interesting and somewhat comical in their behavior, they are also problematic. Only about half of the time will they eat any prepared foods. Instead, they prefer to survive solely on what they can get from rasping the substrate in the display. As such, they tend to do poorly in smaller aquaria (anything under 90 gallons).

I am going to attempt to make a distinction, which may seem like a shade of gray argument to some, but I believe there is an important difference. I do not, nor do I encourage others, to employ these animals to help with a nuisance algae outbreak. They won’t help you do that. But, I believe they are a nice compliment to overall good husbandry in maintaining a beautiful display. To say it another way, they will help the aquarist keep a tank clean, but they won’t clean it for you.

There are a few others that I utilize in my own aquariums. I find Sea Urchins interesting, so I stock them in both my own tank and those of some of my maintenance customers. In my mind, a pair of Bangghai cardinalfish hanging around a commensal long-spine Diadema urchin is on par with Clownfishes and their host anemones. But, I really keep them more for their interesting interactions than for any cleaning duties they perform. That is a distant secondary benefit as far as I am concerned. I also must admit that I added Nassarius Snails to my tank. I keep a lot of sand dwelling cnidarians that I target feed quite a bit. Fungia, Trachyphyllia, Cycloseris, Heliofungia, Alveopora, Catallaphyllia, and a green Carpet Anemone are all part of my collection. The Nassarius snails permit me to be a little sloppy in my feedings, but again, I am not employing them to take care of a nuisance algae problem. I am using them to help me keep things clean along with the sound husbandry practices that I learned long ago. Feel free to use them as well as part of a larger maintenance program.

As for other biological controls, I am generally not a big fan. Pest anemones such as Aiptasia and the so-called Anemonia ‘majanos’ are better dealt with in my opinion and experience via chemical means such as kalkwasser pastes and Joe’s Juice,

http://www.wetwebmedia.com/ca/cav1i3/aiptasia_impressions/aiptaisia_impressions.htm. And, fish parasites are best dealt with using strict quarantine protocols and proven means of treatment:
– Quarantine – http://reefkeeping.com/issues/2004-10/sp/feature/index.htm
– Marine Ich part 1 – http://reefkeeping.com/issues/2003-08/sp/index.htm
– Marine Ich part 2 – http://reefkeeping.com/issues/2003-10/sp/feature/index.htm
– Marine Velvet – http://reefkeeping.com/issues/2004-07/sp/feature/index.htm

When flatworms get this bad in a tank, a thorough review of the husbandry practices and equipment is in order. Pay careful attention to the flow rates of the pumps, feeding amounts and schedule, as well as nutrient export processes.

As for dealing with flatworms, I have to say, I just don’t get it. I don’t understand why people flip out and pour poisons into their reef aquariums in an effort to deal with such a mild nuisance. The common rust-brown flatworms are not parasitic. They don’t do any direct damage to corals or fish. At worst, they are simply unattractive when their population blooms to plague-like proportions. But, they are dealt with easily enough by less drastic means. Manual removal via siphoning and water changes helps tremendously as does making sure the system has sufficient circulation. The aquarist should notice that the flatworms tend to congregate in areas of weak flow. Ensuring that the total flow rate is appropriate as well as making sure the circulation is applied properly creating random, turbulent patterns throughout the display is necessary. Also, check that the maintenance is up to date on all the pumps. I notice the number of flatworms in my own display increases when it is time to clean out the intake screens on the return pumps and give the impellors a vinegar soak to remove deposits. And once this is done, their numbers quickly drop to unnoticeable levels. That makes this yet another instance of a supposed nuisance organism that is easily and best dealt with via normal good aquarium husbandry. No need for additional fishes for biological control or noxious substances added. Just good old simple cleaning practices and your troubles should disappear.

Some people wrongly try to employ the beautiful yet challenging Mandarin fish to aid them in controlling plague-like populations of flatworms when there are far simpler and more effective means.

Steven Pro