Dragonflies or Odonata Anisoptera, are a group of insects belonging to Class Insecta, Order Odonata and Suborder Anisoptera. Considered as ancient, their ancestors were around during the Jurassic Period, along with the dinosaurs. They are predators. Their life cycle breaks down into three distinct stages: the larval stage, the nymph stage and the adult stage. Nymphs can spend a number of years living in fresh water. The adults, which may only last a few days or weeks, can fly. Adults emerge to mate and repeat the dragonfly life cycle. The body length of the average adult dragonfly can vary between 2.54 cm to 10.16 cm. Ancient dragon flies could have a wingspan as large as 70 to 75 cm in extent. The juvenile, dragonfly nymph can range in size between 1.27 cm and 3.81 cm.

The dragonfly nymph is a formidable predator. It spends its life just below the water surface, and has a “hinged labium, a form of a “toothed” lower jaw. It can extend this out every quickly then retract it. This way, the juvenile dragonfly can catch and eat tadpoles, mosquito larvae and even small fish.

Does the dragonfly nymph pose a threat to fish and shrimps in an aquarium? The short answer is definitely yes. There may be as many as 1500 eggs originally hatched. Having come down to us from the Jurassic period, the Odonata Anisoptera juvenile is equipped with the equivalent of a “rapture like lower jaw”. They would have no problems consuming both small fish and shrimps in an aquarium. Bringing fresh water from natural sources may sound a good idea, but there could be a good chance that this could be contaminated with the dragonfly nymph.

Another indication would be that both the small shrimps and fish are showing signs of stress. They are aware that there are dragonfly nymphs in there with them. Removing Odonata Anisoptera may not be that easy once the aquarium is infested with them.

One method could be to use a plastic straw to suck the juveniles out individually. Plants and other water vegetation need to be agitated to get them to move, as the dragonfly nymph can remain very still. Dropping the water temperature in the aquarium by three to five degrees Celsius, might stress shrimps in the tank. This might also bring the dragonfly nymph to the surface.

References

https://en.wikipedia.org/wiki/Dragonfly

https://en.wikipedia.org/wiki/List_of_Odonata_species_of_Australia

http://www.state.ky.us/nrepc/water/dragfly.htm 

Photo Credit: dmills727 Flickr cc

Photo Credit: Exmoor National Park Flickr cc

The Damselfly nymph, Odonata Zygoptera is part of the general group of insects, Class Insecta. Furthermore, they belong to genus Odonata, which also includes dragonflies. Like the dragonfly, the damselfly has very ancient origins, going back to the Lower Permian period.  Both the juvenile nymph and adults are highly predatory. They will eat other insects.

The damselfly nymph is aquatic. It can live in a variety of different fresh water environments. These include rivers, streams, ponds, ditches, quarries and even acid bogs, depending upon the species. The damselfly nymph is subjected to repeated molting. The skin is constantly removed and regenerated. Eventually a “metamorphosis “ takes place, and the final adult damsel fly emerges.

Compared to dragonfly nymphs, the damselfly nymph is smaller, about 15-30 millimeters. Even though it shares a similar extreme predatory nature, its choice of prey may tend to be slightly more restricted. It still might be attracted to crustaceans, such as shrimps, as well as water fleas and mosquito larvae. Again like the dragonfly nymph, the damselfly nymph has a flat labium, or a form of toothed lower jaw. This is quickly released and extended to catch prey.

There is a risk posed to fish and shrimps in aquariums. The damselfly nymph may be less of a threat than the dragonfly nymph, but shrimps and fish larvae may be vulnerable.

However, they are less of a threat than the dragonfly nymph. They may also provide food for the fish in the tank. However, be very careful if you have small shrimps, since these will serve food for this insect.

From various online forums, it seems clear that the plants that are used in an aquarium need to be carefully vetted. This is how the dragonfly and damselfly nymph could possibly gain entry to the aquarium.

References

https://en.wikipedia.org/wiki/Damselfly

http://www.wetwebmedia.com/fwsubwebindex/fwaqinsectfaqs.htm

Photo Credit: postman.pete Flickr cc

Photo Credit: oldbilluk Flickr cc

Planaria is a species of flatworm from the Turbellaria class and is the name for a member of the genus Planaria that is a part of the family Planariidae. It also often refers to the genus Dugesia.

These free-living flatworms have three layers of tissues including an ectoderm, a mesoderm and an endoderm. These three layers of tissues are classified into both organs and organ systems, making flatworms the simplest animals that feature mesoderrmic layers and organ-system levels. It should be noted that flatworms do not have a body cavity, therefore they are acoelomates.

The majority of planarians are freshwater worms that inhabit ponds and streams. However, there are terrestrial and marine species of flatworms, too. Unfortunately for those who have aquariums may find that their aquarium has been plagued by planera, and they can be really problematic.

How Planaria Invade Aquariums

Planaria are a common pest in freshwater aquariums. In freshwater aquariums that house shrimp, planaria often develop as a result of overfeeding. In freshwater aquariums that house other species of fish, they can develop as a result of dirty substrate. When there is either too much uneaten food in an aquarium, or the substrate in the aquarium is not kept clean, the ideal environment for these pests is created. Planaria thrive in these environments, as they consume small shrimps and fish fry.

Are Planaria Dangerous to Fish?

Planaria will not put the fish in an infested aquarium in danger; however, they are very unsightly and can detract from the beauty of a tank. They also are a tell-tale sign of poor tank hygiene and maintenance. If the population of planaria grows to large levels, there is a chance that they could impact the health of the fish that live in the aquarium.

How to Treat a Planaria Infestation

The best way to treat a planaria infestation is avoiding one in the first place. How can you do that? - By not overfeeding your fish and/or shrimp, and by making sure that you properly clean the tank on a regular basis. When cleaning the tank, it is important to clean all surfaces, including the substrate, in order to prevent these pests from developing.

If an infestation of planaria does occur, there are several treatments available. Some of the most common treatment options include:

• Treating the tank with a shrimp friendly chemical dewormer
• Thoroughly vacuuming the substrate in the tank and performing a 30 to 50 percent partial water change.
• Minimize the amount of food being placed in the tank and performing water changes weekly while stirring the substrate.
• Partially changing the water on a constant basis when the tank is overcrowded.
• Using planaria traps

The following article also provides some treatment advice: 

Aquariums make a wonderful hobby. They are soothing, interesting and can provide a lot of fun and entertainment. However, in order to make the most of your aquarium, taking proper care of it is exceptionally important. It must be maintained, and part of proper maintenance is understanding issues that can develop.

One of the side effects of improper aquarium maintenance is the development of pests, and Hydra oligactis – more commonly referred to as just hydra is one of the most dangerous. Also known as freshwater polyps, these pests hail from the Coelenterata family of aquatic invertebrates. They have a tubular body and a sticky foot located on one end and tentacles on the other end. The tentacles contain stinging cells, which the hydra uses to immobilize its’ prey.

Why Hydra are Dangerous in Aquariums

Though hydras are basic creatures that lack a brain, a respiratory system or even musculature, they are a real threat to aquariums. As mentioned, they use their stinging tentacles to immobilize their prey and are able to kill and eat fish fry and even adult fish. Additionally, they reproduce very quickly, creating buds that turn into new hydra that eventually break off on their own. And, though they do tend to stay in one place (using their sticky foot to secure them to a surface,) they can easily move around if they choose.

Given their ability to eat fish, how quickly they reproduce and that they can move about when they want, it’s easy to see why hydra are a real issue in an aquarium.

Treating Hydra in an Aquarium

Once an aquarium has infiltrated an aquarium, they can be hard to eradicate; however, getting rid of them is possible. The treatment for these pests depends on the extent of the infestation.

If the infestation is relatively small, you may actually be able to physically remove them. If they have taken up residence on plants and rocks, they can be killed by removing the plants and rocks and sock them in a solution of 10 percent bleach and 90 percent water for about 15 minutes. After soaking, rinse the plants and rocks with fresh water and let them air dry.

If you are looking for a less intrusive method of removal that will not disturb the aquarium, you can do so by introducing fish that will eat the pests. Mollies, Paradise fish and Spot (blue) Gouramis are known to favor hydra and can rid an aquarium of them.

Heat is another option that can be used to treat an infestation of hydra. With this treatment method, the fish must be removed from the tank first. Once they are removed, increase the temperature of the water to 40°C (104°F) for a few hours. This will essentially cook the hydra and kill them. Turn the temperature of the water down, clean the gravel and change the water. Ensure that the temperature of the water is safe for the fish before reintroducing them.

Chemicals and medicines can also be used to treat hydra; however, do keep in mind that they can be harmful to aquatic life. Copper Sulfate and Potassium Permanganate are two of the most common and safest options in fish only aquariums.

Also take a look at the following article regarding common medication used in aquariums:

Image credit: 

Wikipedia: Hydra oligactis

Hydra are a fresh water animal that belongs to the same group as jellyfish, corals and anemones, The name Hydra stems from Greek mythology. It was the name given to a many headed sea serpent. The hydra that we know resembles this mythological monster by its many tentacles.

Hydra are found in nearly all clean fresh water systems in Australia and around the world . They have a range of colours from brown, green white, and many other variations .

Many people have Hydra in their aquariums, but are unaware of their presence. They are very small approx. 2 - 3 mm in length ( but can extend to around 1cm when hunting) when hanging from the underneath of leaves of water plants are hard to distinguish

A Hydra infestation does not just mysteriously appear in your aquarium and is not caused by poor tank maintenance or anything like that. The animal has to be introduced from some external source.

It is usually introduced to aquariums from plants ,wood, rocks etc collected from wild creeks, rivers lakes and billabongs.

Hydra have a sack shaped body that consists of a mouth /anus combination on the top surrounded by a crown of tentacles that carry an array of stinging cells.

on the bottom of the tube body there is a "foot" ( basal Disk)a device the animal uses to anchor itself to plants ,rocks aquarium walls and the like.

Hydra live attached to vegetation, rocks and walls by this "foot" with all its tentacles suspended into the water waiting for it's pray to blunder into them. Small animals that happen to blunder into the tentacles are stung and paralysed.

within a short time all of the tentacles are wrapped around the victim conflicting many more stings. the victim is then drawn to the mouth and swallowed. Digestion is done over a period of several hours .Any un digested material remaining after this period is then expelled back through the mouth.

The hydra is then ready to hunt again .

It takes several hours for their weapons to recharge which it does while digesting it's food. Small aquatic animals like Rotifers, insect larvae, and ( especially) small crustaceans such as daphnia, seed shrimp and water flee, are their main pray.

Hydra do not always stay in the one spot in the aquarium. they are able to move about in a couple of ways. They are able to secrete a sticky mass under the basal disk and they use this fluid to kind of slide themselves along to a new position. Another way is they detach the basal disk, bend over placing their tentacles on the substrate and then somersaulting re attaching the "foot" further along, they will continue to do this action until they reach their preferred position.

The third manoeuvre noted is that they are able to produce an air bubble in the basal disk this raises them to the top of the water where they hang suspended waiting for pray.

Hydra do most of their reproduction in the summer months. Most reproduction is "A" Sexual and involves a process called "Budding" in which a new Hydra develops as a bud on the parent central column . When conditions are right the bud breaks loose and continues life as an individual. These offspring are genetically identical to the parent ( true clones) .

Under very good conditions hydra may possess several buds at various stages of development. Sexual reproduction is usually confined to the cooler months. Ovaries develop as an oval swelling near the column base. testis form as conical protrusions further up the column the sperm is free floating and can fertilize itself and other hydra. the young develop directly without a larval stage. HYDRA are beautiful but a bit annoying creatures.

Given their reproductive abilities, their capability for moving around when they choose and the ability to eat pray several times their size. it's clear why hydra are not welcome in freshwater aquariums .

They are believed to be able to cause harm or kill newly hatched shrimp, and in laboratory conditions they have been proven to eat baby brine shrimp. Adult shrimp are not effected by hydra stings except possibly as an annoyance. The larger Hydra have also been shown to eat small fish fry as large as newly borne guppies . Once hydra are introduced into an aquarium they can be difficult to get rid of them. ( but it's not impossible) If you are lucky to only have a small infestation you should be able to physically remove them, I removed the infestation that I had by wiping the tank sides down with a clean cloth, removed all rocks ,wood, from the tank and scrubbed them, plants I soaked in a light bleach solution for around 10 minutes before rinsing in fresh water and replacing. Another non intrusive way is to add some fish to eat them Gouramis or mollies will do the trick. ( not a good idea if you keep shrimp).

Heat is another method. ( you have to remove all your livestock to do this) heat your aquarium water to around 40C for about 2 hours. this should kill them, Perform a minimum 50% water change and make sure that the water temp is back to normal before returning your live stock .

Chemicals that can be used are potassium permanganate, or many of the fish anti fluke medications especially if they contain formalin. WARNING THESE CHEMICALS MAY BE HARMFUL TO SHRIMP, SNAILS, PLANTS and sometimes FISH. USE AT YOUR OWN RISK!!!! Some preventative measures are to inspect all live plants carefully( look for small jelly like substances) soak all plants in an approved solution before adding them to your aquarium. Avoid live foods from local rivers creeks etc. Boil all substrate wood rocks collected from the wild before adding to your tank .

References used :- Bugguide Version Jan 2009 Information sources Wikipedia. org/wiki/imdra Williams 1980 Pennak 1989 Gooderham & Syrlin 2002 Offwell Woodland & wildlife Trust UK Researcher Wayne Summerhayes Febuary 2013.

Planaria are usually found in aquariums that have an abundance of uneaten fish food. These animals just don't appear in your tank and must be introduced from an outside source. They are sometimes found just after the introduction of new stock, plants etc. Some people claim that their eggs can be introduced via some forms of flake fish food, or live worms

Planaria are hermaphroditic and carry both male and female organs, they do re produce sexually. These animals more commonly re produce a sexually by a method called TRANSVERSION FISSION. The Planaria will anchor itself by the tail and literally pull itself apart. Over a period of several days the tail section will grow a new head and the head section will grow a new tail. If the animal has a good food source this re production method can be repeated many times. Science has shown that planaria can be dissected up to four separate parts and each section will develop into a full animal. Scientists have also shown that if you divide a planarian's head in two, lengthwise, two heads will develop and the animal will continue life with two heads.

The body of a planaria is non segmented ,The head is triangular shaped and contains two eye spots that detect light, planaria are light sensitive and usually haunt dark areas, and will venture out at night to feed.

Many people claim that planaria are harmless in small numbers and are just an eyesore as they are not active hunters, therefore presenting a very small threat to active shrimp and fish, preferring to feast on the sick and dead.

Most aquarium keepers would rather not have them around because of the fear of their re production abilities. There are several ways that can be put into action to rid the aquarium of these little creatures. The most common methods are listed here.

One of the easiest and non invasive ways, is to keep your tanks clean, vacuuming up all uneaten foods and cleaning the substrate of any detritus, no food no planaria.

Many people opt to tackle the problem by chemical warfare! The most common option is the use of a dog de wormer containing FENBENDAZOLE! the agreed upon "Safe" dosage of Fenbendazole is 0ne gram per 38 litres ( ten gallons) Be sure to remove any carbon that may be in your filters as it will absorb the chemicals defeating the purpose of dosing the tank.

Another method is to build a DIY planarian trap, many ideas for a trap can be found online for example. This trap uses a test tube from a test kit and a small length of air hose. Drill a hole in the lid of the test tube the same size as the air tube push a piece of airline tubing through the hole making sure that the tubing is suspended in the middle of the test tube.bait the trap with a small piece of meat, fish or shrimp etc. submerge the trap and wait check after a couple of days, remove the planaria re bait and set the trap again.

Ref Used www. stevesauter.com/planarians planarians .org

Planarians- Encyclopedia

Planarian - Wikipedia, the free encyclopedia

www, fishtankprojects.com

A healthy ecosystem contains many life forms and not all creatures found in your aquarium are a problem, in fact many are a sign of a well established and healthy tank/ ecosystem. So before you go starting a chemical war with them, take the time to know what it is you are looking at and if they are actually a problem.

Will cause problems for juvenile shrimp in aquariums

Damsel fly nymph (Odonata Zygoptera )

Size range 15 - 40mm

Damselfly Nymphs are easily recognized by their three long tail-like gills at the end of their slender bodies that grow between 16 and 33 mm. They have great vision, due to their large compound eyes. Damselfly Nymphs have extendable jaws that fold up under their head and legs close behind their head. Damselfly Nymphs are predators that feed mostly on other water insects, but they can also be cannibals. Larger species of Damselfly Nymphs can feed on small fish. They catch their food with a toothed lower lip, called a labium. When a small insect comes near, the nymph will shoot out its lower lip to grab its prey.

Dragon fly nymph (Odonata Anisoptera )

Size range 20 - 50mm

Dragonfly Nymphs are short and wide growing 18-49 mm long. They have six legs located near the head, wing pads, and internal gills. Dragonfly Nymphs are predators that feed mostly on other water insects, but they can also be cannibals. Larger species of Dragonfly Nymphs can feed on small fish. They catch their food with a toothed lower lip, called a labium. When a small insect comes near, the nymph will shoot out its lower lip to grab its prey.

Fresh water bristle worm (Annelida Polychaeta )

Size range 1- 100mm

Each Bristle worm has characteristic bristles that are found lining the exterior of their white or pink body. They typically grow between 1 and 100 mm, but have been known to grow up to 150 mm in length. Freshwater Bristle worms can be found in silt substrates and among debris or detritus in ponds, lakes, streams and rivers. They use their two tentacles to capture food or detritus floating by and transport it along cilia to the mouth.

May cause problems for juvenile shrimp if in high numbers

Planaria or flat worm (scientific name)

Size range 0.5 - 15mm

Planarians are usually between 3 to 15 mm with a triangular head that contains two eye spots. The colors vary from white, grey, brown, and black. The mouth is located on the underside of the worm halfway down towards its tail. Planarians suck up seed shrimp, clam shrimp, water fleas, and dead animals using a straw like appendage that extends from their stomaches.

Planarians can regenerate many of their body parts, including their heads!

Hydra (phylum Cnidaria)

Size range 0.2 - 15mm

Hydra has a tubular body up to 10mm long when extended, secured by a simple adhesive foot called the basal disc. At the free end of the body is a mouth opening surrounded by one to twelve thin, mobile tentacles. Each tentacle, or cnida (plural: cnidae), is clothed with highly specialized stinging cells called cnidocytes. Cnidocytes contain specialized structures called nematocysts, which look like miniature light bulbs with a coiled thread inside. At the narrow outer edge of the cnidocyte is a short trigger hair called a cnidocil. Upon contact with prey, the contents of the nematocyst are explosively discharged, firing a dart-like thread containing neurotoxins into whatever triggered the release which can paralyze the prey, especially if many hundreds of nematocysts are fired.Hydra mainly feed on small aquatic invertebrates such as Daphnia and Cyclops.

Not a problem

Nematodes (scientific name?)

Size range 0.01 - 10mm

Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. The total number of nematode species has been estimated to be about 1 million. Unlike cnidarians and flatworms, nematodes have tubular digestive systems with openings at both ends. Nematodes are slender worms, typically less than 2.5 mm (0.10 in) long. The smallest nematodes are microscopic, while free-living species can reach as much as 5 cm (2.0 in), and some parasitic species are larger still, reaching over a meter in length. The body is often ornamented with ridges, rings, bristles, or other distinctive structures.

Tubifex (tubificid annelids)

Size range 10 - 50mm

Tubifex worms feed on decaying organic matter, detritus, and vegetable matter, which is commonly available in sewage/stormwater drains. Tubifex worms are hermaphroditic: each individual has both male (testes) and female (ovaries) organs in the same animals. These minute reproductive organs are attached to the ventral side of the body wall in the celomic cavity. In mature specimens, the reproductive organs are clearly found on the ventral side of the body.

Seed Shrimp (Ostracoda)

Size range 0.2 - 30mm

The body of an ostracod is encased by two valves, superficially resembling the shell of a clam. A distinction is made between the valve (hard parts) and the body with its appendages (soft parts). In most ostracods, eggs are either laid directly into the water as plankton, or are attached to vegetation or the substratum. However, in some species, the eggs are brooded inside the shell, giving them a greater degree of protection. The eggs hatch into nauplius larvae, which already have a hard shell.

Daphnia (Branchiopoda Cladocera)

Size range 0.2 - 5mm

Daphnia are small, planktonic crustaceans, between 0.2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style. They live in various aquatic environments ranging from acidic swamps to freshwater lakes, ponds, streams and rivers.

Cyclops, Copepods (Maxillopoda Cyclopoida)

Size range 0.5 - 5mm

Cyclops or water flea is one of the most common genera of freshwater copepods, comprising over 400 species. Cyclops individuals may range from 0.5 - 5 mm long and are clearly divided into two sections. The broadly oval front section comprises the head and the first five thoracic segments. The hind part is considerably slimmer and is made up of the sixth thoracic segment and the four legless pleonic segments. Two caudal appendages project from the rear. Although they may be difficult to observe, Cyclops has 5 pairs of legs. The long first antennae, 2 in number, are used by the males for gripping the females during mating. Afterwards, the female carries the eggs in two small sacs on her body. The larvae, or nauplii, are free-swimming and unsegmented.

Freshwater Limpet (scientific name)

Size range 0.5 - 5mm

Limpet is a common name for a number of different groups of sea snails and freshwater (aquatic gastropod molluscs). The common name is applied to those snails that have a simple shell which is broadly conical in shape, and either is not spirally coiled, or appears not to be coiled in the adult snail. In other words the shell of all limpets is shaped more or less like that of most true limpets.

Rotifers (scientific name)

Size range Small.

Rotifers have bilateral symmetry and a variety of different shapes. The body of a rotifer is divided into a head, trunk, and foot, and is typically somewhat cylindrical. Rotifers eat particulate organic detritus, dead bacteria, algae, and protozoans. They eat particles up to 10 micrometres in size. Like crustaceans, rotifers contribute to nutrient recycling. For this reason, they are used in fish tanks to help clean the water, to prevent clouds of waste matter. Rotifers affect the species composition of algae in ecosystems through their choice in grazing. Rotifers may be in competition with cladocera and copepods for phytoplanktonic food sources. Rotifers are dioecious and reproduce sexually or parthenogenetically. They are sexually, with the females always being larger than the males. In some species, this is relatively mild, but in others the female may be up to ten times the size of the male. In parthenogenetic species, males may be present only at certain times of the year, or absent altogether.

Most information collected from http://en.wikipedia.org/wiki/Main_Page

Also a great poster for identifying many of the water creatures