Invertebrates in the Aquarium
Aquatic invertebrates are diverse, interesting, colourful and unusual – they can make great additions to your home aquarium. More varieties of freshwater invertebrates are becoming available in the trade, and these creatures can perform several helpful functions in your aquarium.
Invertebrates like snails, shrimp, crayfish and crabs are scavengers that can help reduce the built-up fish food and other waste products, thus making your tank a healthier environment for your fish. When you are looking for a simple way to keep your tank cleaner, consider adding a freshwater invertebrate to your aquarium. Some aquarists who keep freshwater invertebrates actually keep only those invertebrates in the tank, and no fish at all. Freshwater shrimp are a prime example of this.
CRUSTACEANS – crayfish, crabs and shrimps
A large variety of different freshwater crustaceans are now regularly available, they can be divided into five basic types.
- algae-eating shrimps: are mostly small (typically around an 2-3cm in length) and completely peaceful, doing best when kept in groups and maintained in quiet aquaria with small fishes species like tetras and rasboras. They are excellent algae eaters, although they will also take other food like bloodworms and other small, meaty foods (omnivorous). Larger fish will eat these little shrimps, so choose tankmates with care.
- fan shrimps: are fairly large (4-8cm) and robuster in build. In the wild they feed on plankton, but they will also use their fans to collect algae and eat suitable foods from the substrate such as catfish pellets. Fan shrimps are somewhat territorial but otherwise peaceful, and in a large enough tank it is possible to keep multiple specimens. Their larger size makes them a better choice for use with standard community tank than the small algae shrimps.
- long-arm shrimps (Macrobrachium sp.): various types are now available in the hobby. Some species are very large (over 30cm) and all are active omnivores that will consume anything they can catch.
- crayfish are nocturnal omnivores which can feed on soft aquatic plants and dig burrows and uprooting plants. They are also known to catch and eat small fish if they can, and though frequently kept in community tanks they are not really trustworthy in this regard.
- crabs: are similar, but as well as being destructive and potentially predatory, they are also amphibious, and will spend the entire time trying to escape if kept in a normal aquarium. Crabs should be kept only in vivaria where they can move about on land and underwater.
GASTROPODS (snails) and BIVALVES (freshwater mussels and clams)
Snails are unquestionably the easiest maintained invertebrates in an ordinary freshwater aquarium and can be divided up into two groups, those introduced deliberately as novelties, and those that come in as hitchhikers on aquarium plants. Freshwater snails come in a variety of shapes, sizes and colours. Thy are ideal for controlling algae in the home aquarium and they will also scavenge for detritus and leftover fish food.
Apple snails (Pomacea sp.) and Ramshorn snails (Marisa sp.) are the two most common snails in the home aquarium. Apple snails are large and globose, typically about the size and shape of a golf ball, and the varieties sold in aquarium shops have yellow or golden-brown shells. Ramshorn snails are not quite so big and have flat shells about the size of a large coin and are delicately marked with dark brown and yellow stripes. In terms of care these are very similar, requiring tropical rather than coldwater conditions and neutral to moderately hard water. On the plus side, the snails are easy to feed, and will eat a variety of green foods (including aquarium plants) together with catfish pellets and algae wafers.
Pond snails or Tadpole snails (Physa sp.) are perhaps more of a nuisance because they are smaller and more difficult to find and breed much more quickly than other snails. They live in still or slowly flowing waters and have evolved to withstand poor water quality and low levels of oxygen. They breed readily in aquaria, producing clumps of jelly-like egg masses from which tiny but otherwise perfectly formed baby snails emerge.
The Malaysian trumpet snail (Melanoides tuberculata) is a snail that divides the hobby – some aquarists see them as a bonus, others as a pest. On one hand, they are totally harmless as far as plants go, they are excellent scavengers and keen burrowers, and in the planted aquarium do an excellent job of keeping the substrate clean and oxygenated, fulfilling the same sort of role as earthworms do on land. However, they breed rapidly, and any waste organic material in an aquarium not removed by the aquarist will be quickly turned into Malayan livebearing snails. Their strong shells also make them less easily eaten by snail-eating fish. As is often the case, both sides of the divide make valid points, and as useful as these snails can be, it is important not to let their numbers get out of hand.
Freshwater mussels and clams, an often overlooked for the home aquarium, they help to keep aquarium water clean by filtering out detritus and uneaten fish food from the water column. These invertebrates may also help to lower nitrate levels. Clams typically like to bury themselves into the substrate, but if you watch closely you may be able to see their siphon protruding from the substrate. While these invertebrates garner most of their required nutrients from the water itself, you can supplement their diets with quality invertebrate food.
Notes and additional tips
Before you bring an invertebrate home, do some research on the available types of invertebrates. This way you will be aware of any precautions you need to take to protect your aquarium fish and to ensure that you are able to properly care for the creature. While invertebrates mainly feed on leftovers /detritus – it does not mean, that you will not need to supplement their diets, to keep your invertebrates healthy. Most invertebrates are omnivorous and should be offered fresh vegetables and sinking pellets or wafers to supplement their diets. Some freshwater invertebrates (like lobsters) may also feed on the live and frozen foods you offer your fish in your tank.