Invertebrates are animals that do not have any backbone or spine. Familiar examples of aquarium invertebrates include crabs, lobsters and their kin; snails, clams, octopuses and their kin; starfish, sea-urchins and their kin (which includes corals); and worms. The vast majority of animal species are invertebrates and so it’s not surprising that they are a very important part of almost any aquarium system.
To view Freshwater Snails available to purchase go to the Freshwater Snails web page.
Nerita snails, Japanese Trapdoor snails, Assassin snails, and various other snails are commonly available to freshwater aquarists. These are different species than the Asian snails that commonly become a nuisance in freshwater aquariums by hitchhiking on plants. The snails sold for freshwater aquariums will generally not explosively populate the tank and will actually help keep the populations of nuisance snails down. Generally they are compatible in most community tanks although some fish such as puffers will eat snails.
To view Freshwater Shrimp available to purchase go to the Freshwater Shrimp web page.
Unlike Saltwater shrimp which are typically pricey, many types of Freshwater shrimp are both cheap and readily available. These include the common Ghost or Glass shrimp, the Grass shrimp, Japanese Amano Shrimp, the Red Cherry shrimp, the Bee Shrimp, the Singapore Flower shrimp, Red Crystal shrimp, and the Mandarin Shrimp. The Ghost or Glass shrimp will not typically clean algae off of plants like most of the other shrimp will but they are still useful scavengers. Others like the Japanese Amano or Red Cherry shrimp are great additions to planted aquariums and will keep the vegetation free of algae much like Otocinclus catfish will.
To view Freshwater Lobsters available to purchase go to the Blue Lobster web page.
Freshwater “Lobsters” would actually be considered Crayfish by many as the term lobster is usually reserved for saltwater species. It is purely semantic and in the aquarium trade they are typically called “Freshwater Lobsters.” There are several different species of crayfish “lobsters” available for the freshwater aquarium. They make an excellent scavenger for ponds or aquariums and will feed upon any leftover food or detritus that settles on the bottom. They are also algae controllers and will eat any filamentous algae that may form upon the rocks or substrate.
Aquarium Invertebrates – Freshwater Crabs
Surprisingly, there are not really any species of freshwater crabs commonly available for freshwater aquariums that do not require the ability of the crab to get out of the water onto land. However, there are some crabs commonly available to freshwater aquarists such as the Fiddler crab. The Fiddler Crab is a hardy species that does well under proper living conditions. The Fiddler Crab originates from the brackish, inter-tidal mud flats, lagoons, and swamps of Florida. As such, the Fiddler Crab requires some salt in the water in order for it to thrive such as a brackish water tank. The Fiddler Crab is a semi-aquatic species that requires access to an area above the waterline.
To view Freshwater Clams available to purchase go to the Freshwater Clams web page.
While not as colorful or impressive as their saltwater counterparts, freshwater clams are an interesting and valuable addition to the home freshwater aquarium. Two species found are the common Freshwater clam and the freshwater Asian Gold clam. The Freshwater clam is a living filter that helps keep aquarium water clear and clean. By removing uneaten food and detritus from the water column, the Freshwater Clam helps maintain water quality and lower nitrate levels. Like many freshwater bivalves, it typically buries itself in the substrate. However, spotting its siphon protrude from the substrate is truly captivating to observe. The common variety only gets to about 2″, which makes it a suitable addition to well-established aquariums of almost any size.
This is an overview of the Saltwater Invertebrates webpage.
Aquarium Invertebrates – Saltwater Crabs
Saltwater crabs are an almost essential component of a majority of reef aquariums. They are generally hardy and an easy way to keep the tank free of uneaten food and unwanted algae. Dwarf Red Hermit crabs and Blue Legged Hermit crabs are a great addition to any reef tank. Some fish such as puffers or triggers will eat most crabs but there are really large hermit crabs that even they would think twice about approaching. Emerald crabs will eat some algae that other crabs tend to avoid and make a great addition to the tank. The Sally Lightfoot crab is an attractive and entertaining as well as a useful specimen.
Aquarium Invertebrates – Saltwater Snails
Turbo snails, Margarita snails, Cerith snails, Astraea snails, Nassarius snails, and Trochus snails and more are all commonly available to saltwater aquarists. Generally they are very reef safe and compatible in most reef tanks although the same fish that will eat crabs will also eat snails. Some crabs will also predate snails however. They will compete with crabs for algae and food. They are generally affordable and you can keep one every 2-3 gallons of water but most saltwater snails should be given seaweed to supplement their diet if there is insufficient algae in the tank.
Aquarium Invertebrates – Saltwater Shrimp
They tend to be a pricier investment than saltwater snails or crabs but there are many species of saltwater shrimp to add life and color to the saltwater aquarium. They are generally considered reef safe although some have unique requirements and characteristics such as the Camelback shrimp which can nip at corals. Peppermint shrimp are affordable and colorful additions to a reef tank while various types of Cleaner Shrimp will often pick parasites off fish in the aquarium. Some fish such as Hawkfish that will generally stay away from crabs and snails might be more tempted by a shrimp as a snack.
Aquarium Invertebrates – Other Saltwater Crustaceans
Of course, shrimp and crabs are crustaceans but Reef lobsters are sometimes found for sale as well. An ideal environment for a Reef lobster should have a thick gravel bed for burrowing, and rocks for hiding, as well as live rock on which to hunt. After molting, the Reef Lobster will need a secure hiding place, such as a cave, while it waits for its new exoskeleton to harden. The cave can be designed so that the lobster can be seen during the day, but it usually will spend most of the daylight hours hiding from the light. It prefers to scavenge and hunt at night. The Reef Lobster is described as peaceful, and it will ignore sleeping Wrasses or healthy fish within the aquarium.
Aquarium Invertebrates – Starfish
Starfish can also be a great addition to a saltwater aquarium but should be approached with some caution. Most are fairly hardy tank cleaners and reef safe. However, they should never be exposed to air, are generally sensitive to changes in the water parameters, and can be somewhat aggressive, with larger specimens even eating smaller unsuspecting fish. Some like the Red Knob or Chocolate Chip Sea Star often found in stores are definitely NOT reef safe and will feed on and damage corals.
Aquarium Invertebrates – Urchins
Related to starfish, urchins are certainly a fascinating and unusual to have in a home aquarium. However, many species will actually feed on Coralline algae, the pretty purple colored covering the live rock in the tank. Unfortunately, the species that are least suited to the home aquarium are some of the cheaper and more commonly found specimens. Eventually, they will leave tracks all over the live rock and the tank can run out of food for the urchin and it can even be destructive to or eat corals. Other species prefer non-coralline algae to feed on and if you supplement their diet with seaweed sheets then they can be reef compatible. The Blue Tuxedo urchin is said to be completely reef compatible and will not damage live rock or coral although it’s diet should be supplemented with seaweed.
Aquarium Invertebrates – Worms
There are several species of saltwater Fan Worms often found available for the saltwater aquarium. Fan Worms are marine segmented worms that are sessile and attached to rocks or sand by their base. The plume of Fan Worms can measure up to 10″ in diameter on some species. The will require microfauna in the aquarium or supplemental feeding with foods designed for filter-feeding invertebrates.
Bristle worms are often found in the home aquarium and are often considered a nuisance pest hitchhiking their way into the tank on live rock or coral rocks. They are ubiquitous in the earth’s oceans and there are many thousands of species. Bristle worms are actually good tank cleaners but they can grow large enough (up to a foot long or more!) to harm fish and corals in the tank.
Aquarium Invertebrates – Cucumbers
Sea cucumbers are an interesting option for saltwater aquarists. However, if they get sucked into a pump intake by accident there is a possibility they might poison the aquarium. The cucumbers available that do not have branching feeding arms will most likely just disappear under the substrate and live there. They will need a deep substrate and will clean it but you will not likely see them often. The cucumbers with branching arms will likely spend a lot more time out in the open and need microfauna in the aquarium
Aquarium Invertebrates – Scallops
The scallop usually found for home aquariums is usually called the Flame or Red Flame Scallop and has a bright red mantel with red or white tentacles. The Red Flame Scallop builds a small nest of small rocks and pieces of coral in which it embeds itself. In an aquarium, this may not offer much protection. When threatened, it may escape by clapping its valves together, propelling it through the water, with assistance from its tentacles. It tolerates all animals that do not try to eat it, and can be kept in groups. It is a filter feeder, and requires floating micro-plankton to be kept alive in the aquarium, and will do best in a mature reef aquarium system. It also needs proper calcium levels and alkalinity.
Aquarium Invertebrates – Clams
The Tridacna genus has many different species of clams that have become very popular among marine aquarists. The most distinguishing feature of clams is their large two-part shell and interior mantle. Most Tridacna clams have intricately colored patterns in the mantle, making them attractive additions to the marine aquarium.
Tridacna clams can get quite large in nature and have a broad range in the wild. They occupy outer reef habitats on both sandy and hard packed substrates, and can be found either solitary or in small aggregations. Although they can be found in a variety of colorations and patterns in the wild and for sale in the aquarium trade.
Aquarium Invertebrates – Sponges
Sponges are animals of the phylum Porifera (meaning “pore bearer”). They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them. Sometimes a sponge will be offered for sale to the home aquarist. Sponges are found in a wide variety of colors such as red, yellow, and orange and a few different forms. They require a strong current and good water conditions. They can never be exposed to the air. If it is, air becomes trapped in the matrix of channels that line the inside of its body.
Aquarium Invertebrates – Anemones
Many Anemones will host a clownfish just like in that famous movie! However, the commonly found Haitian Anemone and Condy Anemone will not. You also have to get a species of clownfish that is likely to accept an anemone as it’s home. These include Amphiprion clarkii, A. perideraion, A. akindynos, A. rubrocinctus, A.barberi, A. bicinctus, A. ocellaris, and A. percula. Anemones can live singly or in groups in the ocean but typically you will only want one in the tank. This is because they can and will move around and their tentacles can harm corals or other anemones. However, once they find a place they like they will usually stay there.
Aquarium Invertebrates – Cephalopods and other invertebrates
Sometimes other invertebrates are offered for sale to marine aquarists such as Octopus or Sea Slugs. An Octopus requires a very specific aquarium set up in a single species tank and so is only recommended for the absolute most dedicated and advanced aquarists. Sea Slugs are easily sucked into intakes and need algae supplements to survive. It’s best to leave anything too exotic to the real experts.
This is an overview of the Aquarium Microfauna webpage. Aquarium Invertebrates include Microfauna which are microscopic organisms that can play a valuable part in an aquarium ecosystem. These organisms include various species of rotifers and copepods, both fresh and saltwater. Although they are not completely necessary, they will benefit an aquarium ecosystem in many ways when allowed to be present. They act as a nitrogen and nutrient buffer, absorbing nitrates and other contaminants in the aquarium until they can be removed by water changes, filtration, and/or denitrification. They will also help control algae and actually eat many of the organisms that will cause unwanted algae, bacterial (cloudy water), or diatom blooms. In coral reef tanks, they will provide abundant food for corals and other filter feeders. In addition, many fish and virtually all fish fry feed exclusively on copepods, the larger of the microfauna. Copepods in turn feed on rotifers and phytoplankton.
Buying and maintaining beneficial species of microfauna in the aquarium will help crowd and eliminate out possible unwanted species and they will even help control fish disease as the larger numbers of benign microfauna will feed on unwanted and parasitic organisms.
Aquarium Invertebrates – Rotifers
Rotifers are small aquarium microfauna that contain both fresh and saltwater species. They are among the smallest members of the Metazoa — that group of multicellular animals which includes humans, and whose bodies are organized into systems of organs. Most rotifers are about 0.5mm in length or less, and their bodies have a total of around a thousand cells. Their organ systems are a greatly simplified version of the organ systems found in the bodies of the higher animals.
A typical rotifer might have a brain of perhaps fifteen cells with associated nerves and ganglia, a stomach of much the same number, an excretory system of only a dozen or so cells, and a similarly fundamental reproductive system. Despite their complexity, many rotifers are much smaller than common single-celled organisms whose world they share.
Ecologically speaking, this type of aquarium microfauna plays an important contributory role in the natural water purification process. The diet of rotifers also consists of dead or decomposing organic materials, as well as unicellular algae and other phytoplankton. Such feeding habits make some rotifers primary consumers. Rotifers are in turn prey to carnivorous secondary consumers, including shrimp and crabs.
Aquarium Invertebrates – Copepods
Copepods aquarium microfauna are very diverse and are the most numerous metazoans in the water community. Copepods live virtually anywhere where there is water. There are tens of thousands of species. The can be found anywhere from fresh water to hyper-saline conditions, from subterranean caves to water in leaves or leaf litter on the ground and from streams, rivers, and lakes to the sediment layer in the open ocean. The usual length of adults is 1-2 mm, but adults of some species may be as short as 0.2mm and others may be as long as 10mm. Ecologically they are important links in the food chain linking everything from microscopic algal cells to juvenile fish to whales.
Copepods eat and are eaten. Tiny copepods (the smallest look like specks of dust) live most everywhere in the ocean in numbers too vast to count. They’re a key link in ocean food webs. They eat diatoms and other phytoplankton—and are eaten in turn by larger drifters, larval fishes and filter feeders. Copepods may even be the most abundant single species of animal on Earth.
A single copepod may eat from 11,000 to 373,000 diatoms in 24 hours and so are very useful along with rotifers to control a diatom outbreak in the aquarium.
Copepods are tiny crustaceans, so they are cousins of crayfish and water fleas. You can see them with your eyes in the right conditions, but they don’t get much bigger than 2 millimeters. If the aquarium and the room it is in is dark and you shine a flashlight in it you will see them attracted towards the light like moths to a porch light.
Even though there are more insects than any other invertebrates, there really are not any insects commonly kept in aquariums although occasionally an insect larvae might pop up and “water fleas” which are not actually insects but a type of microfauna called isopods that can occasionally get big enough to clearly see with the naked eye are not that uncommon to find. It would be possible to have an aquarium for the purpose of keeping an aquatic insect but generally you would be on your own and hard pressed to find anything commercially available. You’d have to be pretty hard core and dedicated to get into such a thing. Below is a cool video of some isopods in an aquarium. They aren’t actually insects but more closely related to the “Roly-Polys” everyone should be familiar with. These guys would actually make for a good clean up crew … if they don’t creep you out too much! Be forewarned! 😀
Soooo, now we can see why Shrimp, Snails, Crabs, Lobsters, Clams, Starfish, Urchins, and even worms and other invertebrates are more popular choices in most aquariums! However, the invisible, microscopic version of those critters are a great thing to have in your aquarium … I go over those in more detail in the Aquarium Microfauna webpage.