Pictorial guide of hitchhikers


I think a photo guide for freshwater pests, hitchhikers, and other microorganisms would be a helpful addition.

If you have photos of things that have found their way into your aquarium, please share it here. Clear photos are appreciated.

This could help others try to figure out "WHAT IS THIS?!" issues when they come across some creepy crawly, and decide if its harmful, harmless, and ways to eliminate it if needed.

Filling out this info would be great help:

Common means of transfer:
Harmful to:
What to look for:
How to eliminate:


Identity: Bryozoa "Moss Animals"
Common means of transfer: plants, driftwood, possibly from used equipment
Harmful to: nothing, just possibly cosmetic
Benefits: filter feeds particles from water, feeds on cyanobacteria, algae, etc. Food for fish and shrimp
What to look for: almost looks like fuzz or fungus, but closer look shows hard body case with a fan shaped head that retracts into hard body. Fan moves. Lives in a network of connected colonies. It is a type of invertebrate.
How to eliminate: unknown, can survive harsh dry conditions. Survived boiling driftwood. Meds harsh to inverts has not eliminated it. Platy fry have been observed eating it.
Similarities: Can be confused with hydra. Note the bulbous hard shell at base of bryozoa, does not sting, is not mobile as hydra.
Note: can live inside filters.
Further reference: Like hydra but not - Fish, Snail, Worm And Pest ID Help 430760




I can not currently take pics but I can try to find a pic on this forum to use in reference


Pic above taken by JJfishes. JJfishes has allowed the use of this photo in this guide

Pic below take by MissNoodle. Missnoodle has allowed use of these photos also.

Above^^^ Gyro Ramshorn snail. Shell is flat when it is held horizontally to its body.



Identity: Ramshorn snail, Rams Horn Snail

Common Means of transfer: purposely bought, eggs on a plant that you bought, snails on a plant you bought.

Harmful To: Nothing. A peaceful snail. But can grow to large numbers quickly.

Benefits: Great snail to eat up excess detritus and dead plant matter, will consume a level of algae matter too

What to look for: Identified by their signature flat coil shell, looking like a ram's horn, hence the name.

How to eliminate: Assasin Snails, Commercial Products, Or manual removal by means of removing snails by hand and wiping away eggs.

Note- These snails are excellent breeders and can create a large population within weeks. Many fishkeepers consider them pests.


FinalFins id list that they breed fast, and I got some photos of them to add as well when the full guide is made


Look at squiggly thing

Screenshot 2019-11-06 at 8.47.47 PM.png
Identity - Detritus worm

Common means of transfer: just shows up in tanks, transfer of sponge media, transfer of plants/substrate/decor

Harmful to: Nothing. But can endanger fish/other organisms and use up oxygen when in massive numbers

Benefits: Fish will enjoy eating it when it decides to free swim

What to look for: Free swimming worm, swimming in an S shape, tubular. Not to be confused with planaria which commonly stick to glass

How to eliminate- Practically impossible to fully eliminate but to reduce numbers keep a regular water change schedule and gravel vac often and use a turkey baster/syringe to suck up uneaten food from substrate

Note- These often show up when you disturb substrate/during a water change. They live in the substrate.

I’d like to add to this that detritus worms can consume heavy amounts of oxygen from the tank when they are in great numbers. Keep feeding to appropriate amounts to minimize leftovers that would fuel a population growth.


Identity: Bladder snail
Common means of transfer: plants, eggs on plants, sometimes from fish at store
Harmful to: nothing, but breeds incredibly fast. Can clog filters.
Benefits: good cleaners, free snack for some fish
What to look for: jelly like clear masses of eggs on plants, rocks, glass, etc. Have thin long antenna (pond snails have thick triangular antanae). Come in various colours. Stay smaller than a dime.
How to eliminate: snail traps, assassin snails, puffer fish, certain loaches, manual removal.
Similarities: pond snails.



Identity: Great Pond Snail (lymnea stagnalis)
Common means of transfer: eggs on plants, wild plant transfer, deliberate addition
Harmful to: potentially ramshorns should you want them, these snails like to eat ramshorn eggs. Otherwise, not harmful
Benefits: good cleaners, good population control for ramshorns
What to look for: long spiral shell, triangular antenna, no door on shell. Dark brown in colour, reaches 2 inches in length.
How to eliminate: manual removal, assassin snail. Let it die naturally--they need a second snail to reproduce, so a single one will not take over the tank.
Similarities: could be confused with Malaysian trumpet snail (note the door on trumpets), other species in the lymnea family.



Identity: Damselfly larvae
Common means of transfer: plants
Harmful to: small fish, shrimp, fry. Will eat anything, as large or slightly larger to itself.
Benefits: good mosquito control in ponds
What to look for: crawling slender insect with 3 feathered ends to the tail
How to eliminate: manual removal
Similarities: dragonfly larvae.


Adult pictured here



Identity: Scud/Freshwater Amphipod
Common means of transfer: plants
Harmful to: nothing
Benefits: feeds on detritus, free loved food for fish
What to look for: swims sideways, often along bottom of tank. Looks like tiny shrimp.
How to eliminate: predatory fish, copper containing meds.
Similarities: other small freshwater shrimp, shrimplets.



Identity: Trapdoor Snail
Common means of transfer: plants, deliberate introduction
Harmful to: nothing
Benefits: good tank cleaner
What to look for: similar to mystery snail, has door on shell. Shell is spiraled taller than mystery snail.
How to eliminate: manual removal
Similarities: mystery snail, apple snail. Note higher shell and less facial antenna.

Photos are of a young snail hitchhiked on some hornwort. These can grow as large or slightly larger than mystery snails





Identity: Copepods
Common means of transfer: live plant purchase, purposeful addition
Harmful to: nothing
Benefits: consume algae and particulates in the water column. Filter through detritus
What to look for: little white specks. Males look like short-tailed tadpole. Females carry eggs on either side of their rear and so look like a Venn diagram.
How to eliminate: they are crustaceans so anything designed to eliminate them
Similarities: there are several common species who look similar



These are all pictures I've taken in my tank over time
(1) Assassin snail egg laid singularly in a pod also known as a mermaids purse.
(2) Seed shrimp totally harmless but can become a nuisance if you over feed
(3) Copeapod harmless will eat any decaying matter,but if over fed will be a short term nuisance
(4) Fresh water limpet harmless but can be difficult to get off the glass/ also there's a copeapod with eggs
(5) Hydra this taken with a microscope as unseen otherwise, these can be nasty to shrimp of all ages young fish fry
they sting their prey with darts rendering them motionless and certain death. when ready they will break off an arm this will then become a male or female depending what's needed to survive, cutting these into two will only allow them to regrow
(6) Flat worm harmless can multiply very quick
(7) Carpet bug dosnt belong in a tank but this one got in
(8) Planaria from StarGirl15 on fishlore these have a distinct diamond or triangle head although harmless to fish they will eat shrimp making their way into the body by way of under the carapace where the eat their prey from the inside, stargirl found this by isolating her plants to quarantine had she not it would have been a different story so well done to you
(9) Planaria zero this I a powder that will kill Planaria,Hydra,Flatworm,& snails so if you need to use it take out of the tank what you want to live, this powder is my No1 backup.


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As long as all images are your own or you have permission from other members to use theirs then this is a great idea for a thread & could be very helpful for others.
Keeping chit chat to a minimum would be helpful too so the images don’t get lost in the chat,
I’m going to sticky it


Pond/Bladder Snail VS Ramshorn Snail Eggs

Pictures depicting both egg masses to show a reference in case you want to see what you got on a plant.


--loose jelly pouches filled with tiny eggs. Development is fast.
--if removed from water, will look and feel like slime.
--found anywhere, snails have no preference.



--clear or sometimes orange-yellow.
--flat sheet of hard gel. If felt by hand, it is firm rather than blobby like bladder eggs.
--snails prefer to lay on flat surface of rocks, equipment, decor, and plant leaves.
--easily scraped off glass with a credit card or scraper and retains flat shape.
--development of eggs is slower than bladder snails, can take weeks to fully hatch.


If anyone has mystery snail/apple snail or nirite snail egg photos, that'd be awesome to add as well.


Awesome thread.
Suggestion - to add an "AKA" along with the "similar to," e.g. a "Scud" is a freshwater amphipod. This along with the scientific name if it is known for each critter would help folks wanting to do additional research on their own. Of course, some of them (like limpets) will have multiple species names associated.


BLB this is the bug thread


BLB this is the bug thread




Mystery snail egg clutch laid above water line. Hardens after a day and will hatch around 2 weeks give or take depending on temperature. If unwanted, just pop it off after it has hardened and throw it away.


Adding some further examples of bryozoa (see second post to this thread)

Video of a colony in a blackwater setup.



Bryozoa on an anubias leaf, being disturbed. Showing behaviour of this animal.



Ramshorn eggs on an anubias leaf, showing the distinct flat shape and an orange tint


Same eggs, freshly hatched.


Freshly hatched snails could easily be mistaken for things such as fish eggs.


Identity: Cadisfly Larvae
Common means of transfer: plants (hornwort seems to be a common one)
Harmful to: unknown
Benefits: unknown
What to look for: a tube of plant that swims, has a worm on the wider end.
How to eliminate: manual removal
Similarities: possibly other aquatic fly larvae




Nerite snail eggs. Nerites lay them indiscriminately, and no they will not hatch and take over your tank with adorable nerites.



Identity: Leech (egg sacs and young)
Common means of transfer: plants, rocks, driftwood
Harmful to: depends on species, some harmful to fish and inverts.
Benefits: potential live snack to some fish
What to look for: clear or fuzzy sacs attached to surfaces or plants
How to eliminate: manual removal
Similarities: young may be confused with other small worms. They move by grasping one end and scooting the back end forward. May swim similarly to a detritus worm. Unmistakable as an adult. Look for round disc on one end of body--this is the sucker.

Photos courtesy of Laur


Video of adult leech behaviour (pardon background noise)

Adult leeches (photo: JazzieGurl )


Adults with egg casings (JazzieGurl )






Identity: Midge (larvae), many species
Common means of transfer: Used filter media or ornaments with larvae, open windows for adults to enter home
Harmful to: not much, depending on species. Harmless to fish and inverts.
Benefits: snack for fish
What to look for: strings of debris inside filter and in areas where detritus collects.
How to eliminate: unknown
Similarities: detritus worms, but note that detritus will not construct tubes out of detritus to live in like some midge larvae.

^inside algae jar with larvae within the tubes visible. If disturbed they will fall out of the tubes.

^ tubes on filter tray.

They got into my algae growing jar. Feeding off the algae in the water. Note the detritus tube is green because of the diet of algae. This is normally brown.

^adult in my house plant


Identity: Unknown Annelid Worm
Common means of transfer: unknown
Harmful to: depends. Leeches are considered in this broad family group. This particular one is harmless.
Benefits: snack for fish
What to look for: thin worm, reminiscent of detritus worm but with segments, legs, or hairs on length of body.
How to eliminate: unknown, unless fish prey upon them (see video)
Similarities: detritus worms, flatworms. Note jerky movements while moving more like an earthworm along glass. Note faint "hairs" on side of worm (difficult to see). Will not appear as smooth as detritus worms or flatworms.

Video showing movement


Springtails : Collembola
Springtails - Isotomidae family (elongated bodied variety). From the genus Isotomurus (there are many more genera often found).
Common means of transfer: Usually floating plants. Emersed plants. Leaf litter.
Harmful to: nothing.
Benefits: Great snack for fish that feed from the surface. Eats dead plant matter, fungus, algae and microorganisms from floating plants and the brace of a tank.
What to look for: Springtails are hexapods, so they will have six legs. Can come in a variety of colours, yellow, black, blue, orange, green and more. Some are patterned and young springtails are incredibly small and white, though otherwise they resemble adults. They don't enter the water column, they stay on the surface of the aquarium and are often found on floating plants and the brace of a tank. They will congregate in moist areas. When spooked they will use a specialized appendage called a furcula, which is folded under the abdomen, to quickly spring up to 4 inches from the threat.
How to eliminate: Increase surface agitation. Some people use a hair dryer to fry those that they see.
Similarities: Fleas, aphids. Unlike fleas which have large hind legs designed for jumping, springtails have normal hind legs. Fleas will be brown and flat side to side, while springtails have a rounder body and come in many colours. Unlike springtails, aphids have more of a pear shape to them.

Adult on my brace (I gave them some moss...)


Younger Springtails (and another springtail variety I'll talk about later)

Adult on my floating water sprite:


Identity: Globular Springtails - Sminthuridae family.
Common means of transfer: Same as above.
Harmful to: nothing
Benefits: Same as above, only cuter.
What to look for: Springtails are hexapods, so they will have six legs. Unlike the long bodied members of the Isotomidae family, globular springtails are speherical and more compact. Adults are smaller than their long-bodied counterparts. Their movements are the same as those above. They spend their time on floating plants and braces of tanks and can spring when threatened. These guys are much more numerous in my tank, especially on my plants. The longer-bodied springtails seem to be more numerous on my brace.
How to eliminate: Same as above
Similarities: Same as above.

(I'll see if I can get better pics when I get a better camera)
Globular springtails on my brace enjoying their moss:


Two springtail types together, the elongated bodied springtail isn't an adult


Group photo, elongated are more numerous in this pic (and they appear in different stages of their life), but there is a Glob beside the adult.



Thinking I should add this link to this thread, very helpful ID site.

Macro photography of freshwater invertebrates.
The link hasn't worked can you repost please


Identity: Vorticella - genus
Common means of transfer: Pond water, other
Harmful to: Shrimp, possibly small fry if it clogs their gills/lungs
Benefits: Infusoria, detritus/filter feeding cleans water
What to look for: White cloud like spot or ring on glass/substrate that occasionally contracts. Cillia appendages.
How to eliminate: Wipe off
Similarities: Potatozoa, cilliates, looks like mold or bacteria growth but moves.


Although not that common the Oribatid mite is harmless likes to eat the edges of my plant leaves but no real damage as they are so small you'll need a magnifier or macro lens to id them


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As post #25 above by missnoodle, I beileve I have found midge larvae in shrimp tank, through my own research I believe glassworm/ phantom midge
All I can say is they have a very weird way of moving through the open water when they do, like a spring coiling up and uncoiling with a very fast flicking motion.
I can only hope they are eating the abundant seed shrimp and not my baby neos.
Photo with macro lens
20210713_160952.jpgHatched one floating on surface.


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