[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 maxillopod crustaceans 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 flatworms 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
Ostracods are tiny crustaceans 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 insects 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.

This post has been edited by TylerFerretLord: 16 April 2009 - 10:07 PM

[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 insects. 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 insects. 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 branchiopod crustaceans, 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 cnidarians. Is biologically immortal. 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 crustaceans in the order Amphipoda 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 branchiopod crustaceans generally found in small temporary pools of water. Feed on algae and detritus. Superficially similar to bivalve mollusks, hence the name. Link.

This post has been edited by TylerFerretLord: 01 August 2009 - 04:15 AM

[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 insects. 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 insects 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 isopods, crustaceans 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 insects. 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 insects. 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 branchiopod crustaceans 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 insects 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 insects 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 insects 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 insects that are commonly found skating around the surfaces of ponds. Feed on insects that get stuck in the water. Link, Identification help.

This post has been edited by TylerFerretLord: 23 September 2009 - 02:36 AM

[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]

This post has been edited by TylerFerretLord: 03 April 2009 - 04:01 AM

[milkton]

amazing...

[BenPursglove]

milkton, on Mar 22 2009, 08:43 PM, said:

amazing...

Indeed it is and should in my opinion be pinned.

[craftycarper52]

this should defo be pinned. lost count of the times when i have tried to identify creepy crawlies in my tank

[DiscusKeeper403]

Arg. This is making me angry this hasn't been pinned yet. Good information like this is wasted and it will quite possibly deter people from writing out good information for the rest of us to benefit from.

[silverrabbit]

This would have been extremely useful when I found creepy crawlies in my tank the other day. Please let it be pinned.

[three-fingers]

I agree it should be pinned, it covers so many commonly asked questions,and is well written and comprehensive.

Has anyone asked a mod if it can be pinned?

I think it should go in 'General, Faq, Topics And Guides, Links and index in here' as well as the 'Invertebrates, Amphibians & Aquatic Reptiles Forum'.

[DiscusKeeper403]

Tropical fish emergencies IMO. Rdd1952 was supposed to pin it....

[TylerFerretLord]

Oh man, just learned about the acronym tag. Gonna add some stuff with it.

[DiscusKeeper403]

Ill put it in my sig until it gets pinned. In big font for all the mods to see

[Amunet]

Very nice thread. I gotta say though.... if I ever saw one of those giant water bugs in my tank I would scream bloody murder!

[Rexx0rz]

omg, now i'm scared, i really hate insects, i'm never getting live plants D:

*dies*

[TylerFerretLord]

Not need to be so drastic. Chance of getting a water bug is really low.

[Amunet]

TylerFerretLord, on Apr 8 2009, 02:57 PM, said:

Not need to be so drastic. Chance of getting a water bug is really low.

Lol figured that much, just saying.. that is one scary looking bug, and knowing that they bite makes them even worse

[Syphoniera]

Thanks so much for this wonderful compilation, TylerFerretLord, both interesting and useful.
It certainly should be pinned, as should you, only with a medal, in your case.

[pippoodle]

pin it great write up

[TylerFerretLord]

Getting ready to add a couple of beetles, and I was wondering if you folks think I should add a listing for algae? It would either be a single entry with a link to an algae identification guide or an entire section with individual listings.