Hitchhikers In Freshwater Tanks & Ponds

[TylerFerretLord]

Freshwater ecosystems are much more diverse than our tanks can ever be, but nature certainly tries. Here's a list of things that can pop up in a tank unexpectedly.

COMMON HITCHHIKERS

Freshwater copepods(Cyclops)

*
Subclass Copepoda
Danger: Harmless.
How it gets in your tank: Food, Water, Plants, Fish, Live food, Sediment.
Size: ≤ 1mm
Most freshwater copepods are tiny and harmless white/cream [acronym="Maxillopoda is a class under the phylum Arthropoda, subphylum Crustacea, and is characterized by a reduction of the abdomen and its appendages."]maxillopod[/acronym] [acronym="Crustaceans (Crustacea) are a large group of arthropods, comprising almost 52,000 described species, and are usually treated as a subphylum. They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles. The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs and woodlice. Crustaceans are among the most successful animals, and are as abundant in the oceans as insects are on land."]crustaceans[/acronym] that swim around and crawl on surfaces in a jittery fashion. Those that are detrimental are parasites that bury into flesh, but these are obvious on fish. The images show the general shape of a harmless copepod magnified. Fish eat them up. Link.

Snails

Class Gastropoda
Danger: Generally harmless. Some may eat plants.
How it gets in your tank: Plants, Live food.
Size: Varies
See this thread Large numbers caused by overfeeding or introducing to a long-established tank. Most make good additions to a tank.

Planaria

Family Planariidae
Danger: Harmless.
How it gets into your tank: Plants, Water, Live food.
Size: Generally ≤ 4mm
Planaria are non-parasitic [acronym="The flatworms, known in scientific literature as Platyhelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals."]flatworms[/acronym] often seen in new tanks. Large numbers of them are indicative of overfeeding or decaying animal matter being in the tank. Often seen crawling on glass.

Ostracods(Seed shrimp)

*
Class Ostracoda
Danger: Harmless.
How it gets in your tank: Plants, Water, Live food, Sediment.
Size: Generally ≤ 2mm
[acronym="Ostracods are small, laterally compressed and protected by a bivalve-like, chitinous or calcareous valve or "shell". The hinge of the two valves is in the upper, dorsal region of the body."]Ostracods[/acronym] are tiny [acronym="Crustaceans (Crustacea) are a large group of arthropods, comprising almost 52,000 described species, and are usually treated as a subphylum. They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles. The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs and woodlice. Crustaceans are among the most successful animals, and are as abundant in the oceans as insects are on land."]crustaceans[/acronym] that occur in nearly every aquatic environment. May swim around in a jittery, looping fashion or walk on surfaces. Feed on algae, detritus. Link.

Bloodworms

Family Chironomidae
Danger: Harmless. Turn into annoying insects.
How it gets into your tank: Live food.
Size: ≤ .5inch
Bloodworms are the larvae of non-biting midges often sold as live food. Float around at the surface. Link.

Blackworms

Family Lumbriculidae
Danger: Harmless.
How it gets into your tank: Live food.
Size: ≤ 1inch
Blackworms are frequently sold as live food. Harmless detritivores.

Mosquito Larvae

Family Culicidae
Danger: Harmless. Turn into annoying insects.
How it gets into your tank: Live food, Mosquitoes laying eggs in tank.
Size: ≤ .5inch
Mosquito larvae are [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym] sometimes sold as live food. Float around at the surface.

Tubifex worms

Genus Tubifex
Danger: Harmless.
How it gets into your tank: Live food, Plants(unlikely).
Size: ≤ 1inch
Tubifex worms are often sold as live food. Usually stay buried in the substrate with one end sticking out for respiration. Link.

Misc. 'Wormy things'

*
Various groups
Danger: Generally harmless.
How it gets in your tank: Plants, Fish, Water, Live food.
Size: Often ≤ 4mm
Can be any number of thing. Large numbers may be indicative of overfeeding. Many stay in substrate.

 

[TylerFerretLord]

UNCOMMON HITCHHIKERS

Leeches

Subclass Hirudinea
Danger: Varies. All are predatory.
How it gets in your tank: Plants, Live food.
Size: Varies, often small
All leeches prey on other animals. Most are predators of worms or other invertebrates. Few are bloodsuckers. Leeches can be identified as having segmented bodies with a sucker on each end. Link.

Dragonfly nymphs

Suborder Epiprocta
Danger: May consume very small fish, Fry, Shrimp.
How it gets in your tank: Plants, Live food, Dragonflies laying eggs in your tank(unlikely if indoors).
Size: Often ≤ 2inch
Larval stage of dragonfly life cycle, are [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym]. Have extendable jaws. Live underwater for several years before turning into adults. Link, Identification Help.

Damselfly nymphs

Suborder Zygoptera
Danger: May consume fry.
How it gets in your tank: Plants, Live food, damselflies laying eggs in your tank(unlikely if indoors).
Size: Often ≤ 2inch
Larval stage of damselfly life cycle, are [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym]. Have extendable jaws. Live underwater for several years before turning into adults. Have a three pronged 'tail'. Link, Identification Help.

Daphnia(Water fleas)

*
Order Daphniidae
Danger: Harmless.
How it gets in your tank: Live food, Plants(unlikely), Sediment.
Size: Usually ≤ 2cm
Daphnia are [acronym="Branchiopoda is a group of primitive and primarily fresh water crustaceans, mostly resembling shrimp. There are over 900 known species worldwide."]branchiopod[/acronym] [acronym="Crustaceans (Crustacea) are a large group of arthropods, comprising almost 52,000 described species, and are usually treated as a subphylum. They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles. The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs and woodlice. Crustaceans are among the most successful animals, and are as abundant in the oceans as insects are on land."]crustaceans[/acronym], often fed to small or picky fish. Swims around in a hopping movement. Not likely to be encountered in a tank with fish. Feeds on algae blooms. Link.

Hydra

*

Family Hydridae
Danger: May consume fry, Tiny shrimp. Harmless to adult fish and shrimp.
How it gets into your tank: Plants, Live food.
Size: Generally ≤ 1inch
Looks similar to an anemone and stays attached to surfaces. One of the few freshwater [acronym="Cnidaria is a phylum containing some 9,000 species of animals found exclusively in aquatic, mostly marine, environments. The name Cnidaria comes from the Greek word "cnidos," which means stinging nettle. Their distinguishing feature is cnidocytes, specialized stinging cells that they use mainly for capturing prey."]cnidarians[/acronym]. Is [acronym="Biological immortality can be defined as the absence of a sustained increase in rate of mortality as a function of chronological age. A cell or organism that does not experience, or at some future point will cease aging, is biologically immortal."]biologically immortal[/acronym]. Feeds on tiny animals and photosynthesizes. Link.

Gammarus(Scuds)

Suborder Gammaridea
Danger: Harmless.
How it gets into your tank: Live food, Plants.
Size: Generally ≤ .5inch
Gammarus are [acronym="Crustaceans (Crustacea) are a large group of arthropods, comprising almost 52,000 described species, and are usually treated as a subphylum. They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles. The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs and woodlice. Crustaceans are among the most successful animals, and are as abundant in the oceans as insects are on land."]crustaceans[/acronym] in the order [acronym="Amphipoda (amphipods, also sometimes known as scud) are an order of animals that includes over 7,000 described species of shrimp-like crustaceans ranging from 1 mm to 140 mm in length."]Amphipoda[/acronym] that prefer to hide under rocks or wood. They are often sold sun-dried, but sometimes show up in live-foods. Will be eaten by fish quickly. Feeds on algae and detritus. Link.

Springtails

Subclass Collembola
Danger: Harmless.
How it gets into your tank: Wild springtails coming into your home, Floating plants.
Size: ≤ 2mm
The springtails we may find in our tanks will float at the surface or rest on plants. Feed upon surface films and fungi.

Clam shrimp

Orders Cyclestherida, Laevicaudata & Spinicaudata
Danger: Harmless.
How it gets into your tank: Plants, Sediment.
Size: ≤ 15mm
Clam shrimp are small [acronym="Branchiopoda is a group of primitive and primarily fresh water crustaceans, mostly resembling shrimp. There are over 900 known species worldwide."]branchiopod[/acronym] [acronym="Crustaceans (Crustacea) are a large group of arthropods, comprising almost 52,000 described species, and are usually treated as a subphylum. They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles. The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs and woodlice. Crustaceans are among the most successful animals, and are as abundant in the oceans as insects are on land."]crustaceans[/acronym] generally found in small temporary pools of water. Feed on algae and detritus. Superficially similar to bivalve mollusks, hence the name. Link.

 

[TylerFerretLord]

RARE HITCHHIKERS

Caddisfly larvae

Order Trichoptera
Danger: Generally harmless. Some species are predatory.
How it gets into your tank: Plants
Size: ≤ 1inch
Caddisfly larvae are known for the cases they make from sand, pebbles, bits of plants(as depicted) and even snail shells. Are [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym]. Most caddisfly larvae are harmless detritivores, but a few species are predatory on other invertebrates. Generally, the predatory species do not make cases. Link, Identification help.

Giant water bugs(Toe-biters)

Family Belostomatidae
Danger: Preys on small fish, shrimp. Can give extremely painful bite.
How it gets into your tank: Plants, Wild insects coming into your home.
Size: Generally ≤ 2inch
Large aquatic [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym] that feed on small animals. Males carry eggs on back until hatching. Can play dead if scared. Link, Identification help.

Asellus(Water slater, Hoglouse)

Family Asellidae
Danger: Harmless.
How it gets into your tank: Live food, Plants.
Size: Generally ≤ 1inch
Asellus are [acronym="Isopods are an order of peracarid(in the superorder peracarida) crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek iso meaning "same" and pod meaning "foot"."]isopods[/acronym], [acronym="Crustaceans (Crustacea) are a large group of arthropods, comprising almost 52,000 described species, and are usually treated as a subphylum. They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles. The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs and woodlice. Crustaceans are among the most successful animals, and are as abundant in the oceans as insects are on land."]crustaceans[/acronym] related to terrestrial pill bugs. Harmless detritivore. Link, Video, Identification help.

Alderfly, dobsonfly & fishfly larvae

Order Megaloptera
Danger: Generally feed upon other insect larvae. Unknown if they will attack fish or shrimp.
Size: ≤ 3inch
How it gets in your tank: Plants.
Larvae of megalopteran [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym]. Can possibly give a painful bite. Live underwater for several years before pupating. Likely harmless, but this is a sizable group. Link, Identification help.

Stonefly larvae

Order Plecoptera
Danger: Generally harmless.
Size: ≤ 2inch
How it gets in your tank: Plants.
The larvae of stoneflies, which are small flying [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym]. Usually feed on algae, detritus, sometimes other larvae. Possess two caudal filaments. Link, Identification help.

Freshwater fairy shrimp('Sea monkeys')

Order Anostraca
Danger: Harmless.
How it gets into your tank: Food, Live food, Sediment.
Size: ≤ .5inch
Fairy shrimp are [acronym="Branchiopoda is a group of primitive and primarily fresh water crustaceans, mostly resembling shrimp. There are over 900 known species worldwide."]branchiopod[/acronym] [acronym="Crustaceans (Crustacea) are a large group of arthropods, comprising almost 52,000 described species, and are usually treated as a subphylum. They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles. The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs and woodlice. Crustaceans are among the most successful animals, and are as abundant in the oceans as insects are on land."]crustaceans[/acronym] that include brine shrimp. Swim around. Sometimes fairy shrimp eggs will hatch when trying to hatch triops. Will become fish food or get sucked into filters. Link.

Water scorpions

Family Nepidae
Danger: May feed on small fish, shrimp.
How it gets in your tank: Plants.
Size: ≤ 1inch
Water scorpions are small aquatic [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym] that prey on small animals. Get their name from the tail-like breathing tube. Can bite. Link, Identification help.

Water boatmen

Family Corixidae
Danger: Generally harmless.
How it gets in your tank: Plants.
Size: ≤ 2 inch
Small aquatic [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym] that feed on algae and plants. Swim at the water surface. Often confused with backswimmers. Link, Identification help.

Backswimmers

Family Notonectidae
Danger: May prey on small fish.
How it gets in your tank: Plants.
Size: ≤ 2inch
Small aquatic [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym] that feed on other insects and fish. Swim at water surface upside down. Often confused with water boatmen. Identification help.

Water striders

Family Gerridae
Danger: Harmless.
How it gets in your tank: Plants.
Size: ≤ 1inch
Water striders are small [acronym="Insects (Class Insecta) are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles. With over a million described species—more than half of all known living organisms—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans."]insects[/acronym] that are commonly found skating around the surfaces of ponds. Feed on insects that get stuck in the water. Link, Identification help.

 

[TylerFerretLord]

*= Image used with permission from Liam.

WHAT TO DO

Well, hopefully by now you've identified what has decided to live in your tank, but what do you do next? That would depend on what you've found. The small harmless(and honestly beneficial) things, such as copepods, ostracods, scuds and asellus are better left in the tank. They feed on leftover food and algae and are eaten by the fish. Snails should also be left in the tank assuming they aren't damaging plants. If they reach large numbers just sit it out and wait for the population to drop as well as making sure that you aren't over feeding.

What of the wormy things? These are quite often harmless and stay in the substrate, breaking down waste into a form usable by plants. Occasionally you may see one drifting in the current after being dislodged from the sediment; These will often be eaten by your fish. Planarians are also mostly harmless, and may be indicative of overfeeding if present in large numbers. Leeches, however are a mixed bag. They are all predatory, mostly upon other invertebrates, but some will attack and possibly kill fish. If you see a leech in your tank it is best to isolate it and try to get an identification on it. If it will not prey on your prized fish or other stock, it can be safely returned to the tank if you wish and can make an interesting addition.

The predatory insects should be removed from the tank if you have fish or other stock that they can prey upon. These can make interesting pets in their own right, and most can be happily housed in a ten gallon with a sponge filter and some easy to grow plants. Be warned that many are adequate fliers and are attracted to bright light, so a cover should be used. The insects that will not prey on your stock can be kept in the tank if you so desire, but the carnivorous species need to be fed if you want them to survive.

FURTHER READING

General identification and information:
Tree of Life project(Wonderful, highly informative site. Recommended read.)
Aquatic invertebrates of Alberta(good info on many groups).
Pond life identification.

On crustaceans:
More on Branchiopoda.
Crustacea.net

On insects:
For identification of insects and bugs.
General info on aquatic insects.
Identifying aquatic insects.
The world of aquatic insects.
Common aquatic insects.
More on aquatic insects.
Identifying aquatic insects from your pond.[.PDF]

 

[TylerFerretLord]

ew!!!!

I... Can't... Stand... bugs.
'Ew' is right!

They're coming for you. The insects are coming for you.

Run. Drop everything you're doing and run. You don't have enough time to pack, just run if you want to survive.

 

[Flute]

I've just bought 2 Pearl Gourami's from my local LFS and now having floated them in the tank spotted that one of them has a hitch hiker on her head. I don't think it's anything listed on here though. It's moving around quite a bit, it's very flat, a cloudy white in colour and has what looks like lots of little feathery legs. It actually kinda looks like a flat fish in shape.

Can anyone give me any ideas as to what it could be? Am going to go get my quarantine tank set up now and will put them both in that. Do you think I'll have to dose them with anything, or will it eventually just fall off? Don't want to risk infecting my tank though.

Thanks for any ideas!

 

[blue acara]

Might want to add this to the list.

Common name: Fish mite, water mite
I dont know exact latin name

These things live just above the water. They appear red in the pics but this is because of the light they were under...they are translucent. They are tiny at 0.5 mm or less. They seem to feed on algae or any fish food left near where they live. They are extremly fast and can jump, they float on the water surface but dont swim underwater that ive seen. They are extremly annoying and disgusting little things. While doing tank maintenance they can get on you and they ich probably by biting.

Danger to fish: unlikely but I cant say for sure

pics:

 

[Kirsty5]

Having found numerous creepy crawlies in my tank as mentioned here, I thought I'd seen them all until I caught a glimpse of a nasty the other day, thanks to this, i immediately recognised it as a dragonfly larvae and hoiked it out - gross beastie......... Nice out in the countryside but not nice in my tank with little fishies

This video link is interesting if you find one in your tank

http/www.youtube.com/watch?v=Ezq_JWd1Sd8&feature=fvw

 

[OldMan47]

Faffer, dragonfly and damselfly larvae are dangerous in a tank. They eat lots of small fish like fry. Mosquito larvae are great fish food. You need to identify what you are seeing.