AHABS... Issue Six

True Grit: Sand, Science, and Aquaria


Ronald L. Shimek, Ph. D.

In The Beginning…

In addition to invertebrate animals and aquaria, one of my other interests is history. I enjoy reading about some types of events or various periods and seeing what, if any, insight seems to be shed on the events by various historians. I have even, in a few somewhat hysterical flights of fancy, considered writing historical commentary of a few events myself. Probably because of my interest in history, and although I guess it should come as no surprise, I continually have to remind myself that many aquarists apparently have no conception of the consequences of the passage of time or of the temporal requirements of accumulating the information that they seek. I suppose this is partly a result of living in the beginnings of the age of digital information retrieval. In search of answers many, perhaps most, aquarists and students, for that matter, have become conditioned to doing a simple online search and considering the results obtained as “the whole and definitive story.” The ease of access and the immense breadth of online information have conditioned people to expect to be able to turn up an answer to any question they pose.

And an answer they often get.

Unfortunately, the immense breadth of online information is often only matched by its immense shallowness; as the old pioneers said about the Platte Rive, “It is a mile wide and an inch deep.”

After intensive study, and a great deal of research, started and concluded, in good internet...



Ronald L. Shimek, Ph. D.

For several years, I have been recommending and suggesting that aquarists add “detritivores” to their sand beds and to their reef systems, in general. A short time ago, I got asked, “Just what is a detritivore and really why should I add some to my tank.” In essence, the aquarist wanted to know why in the world that they should pay a lot of money for animals that generally are invisible. And even worse, why pay for animals that when they are not invisible are ugly?

Well, I thought the answer was obvious. Then, I thought, well maybe it is obvious if you are a marine ecologist who has spent a lot of time working with these kinds of animals. But for the average hobbyist, the questions I was asked are really pretty good ones, and definitely raise some valid points.

To get to the end of this discussion, and to answer those questions, though, I need to start with the concept of detritus and discuss it. I will then discuss several different kinds of detritivores and their importance to marine aquaria.

Detritus - A Multitude of Sins

As words go, “detritus” is nice; it is short and even I can spell it correctly, at least most of the time. The word is concise and easy to say. Only its meaning is ambiguous. The term “detritus” is actually a word of Latin derivation and it means a “rubbing or wearing away.” As is generally understood, detritus is fine particles eroded off larger particles, or in our systems, the small particulate material resulting from either the biological or...

Tanaids in Reef Aquaria


Ronald L. Shimek, Ph. D.

Aquarists are generally familiar with some of the larger crustaceans such as the hermit crabs or various shrimp species found in their aquaria. Other than the animals that are added to aquaria by the hobbyist, though, there are a quite number of smaller bugs that seem to show up more-or-less by themselves. These immigrants make their largely unpredictable appearance by arriving as hitchhikers or wayward travelers in or on live sand, live rock or on decorative animals such as corals. Almost always, the first of the microcrustaceans to be seen in reef aquaria are the harpacticoid copepods. Visible only as tiny white dots moving on the aquarium walls, they also form swarms in the water, but as these animals are more-or-less natural fish food, such “pelagic” aggregations are largely absent in tanks with fish in them.

Although the harpacticoids are almost always the first of the smaller crustaceans to show up unbidden in our systems, three groups of slightly larger crustaceans also have representatives commonly found in our aquaria. These groups are the Mysidacea ; also known as “the possum shrimps,” or “mysids;” the Amphipoda; also known as “scuds,” “side-swimmers,” or “amphipods” and the Isopoda; also known as “pill bugs,” “rolly- pollies ,” or “isopods.” These three groups have a lot in common and are actually probably closely related. Taxonomists put them all in the group called the “Superorder” Peracarida, in the great assemblage of animals referred to as the taxonomic hierarchical group referred to as the “Class” Malacostraca.

Taxonomic “Classes” are groupings that are subdivisions of the largest taxonomic unit, a “Phylum,” within a kingdom. A phylum is easiest conceptualized as a basic and unique way of making an animal, or put another way, a discrete body architecture with a consistent set of characteristics. Classes are subdivisions of that body plan that are consistent unto themselves. As an example, all birds can be grouped into the Class Aves of the Phylum Chordata. Other groups of Chordate species at the Class level include the Mammalia, or mammals, and the Reptilia, or reptiles. Likewise there are many other Crustacean classes, such as the Class Cirripedia , the barnacles, and the Class Copepoda , a group that contains, not too surprisingly, the copepods. However the largest crustacean class, and really the most diverse crustacean group in forms of body structure, is the Class Malacostraca...


Ron Shimek