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What's that bug? How to recognize them

267K views 373 replies 173 participants last post by  Arty and Noodle 
#1 · (Edited)
I don't know if this belongs under "Shrimp" or "General Planted Tank Discussion", the questions about tiny aquatic creatures might usually be posted in the latter one, but I've always used to put shrimp, other invertebrates, bugs and weird things under same classification.

Here's some of the most common tiny creatures found from the aquariums.

Copepods, Cyclops



Size: 0,1 - 0,2 cm, 0.04 - 0.1 inches

Copepods are small and funny looking one eyed crustaceans. They usually move around the tank glass and other surfaces, usually with one short leap at a time. Harmless, cute, there's lots of different coloured species.

Water Fleas, Daphnia



Size: 0,1 - 0,5 cm, 0.04 - 1/4 inches

Water fleas are usually used as fish food. They are tiny crustaceans and are easily recognized of their jerky vertical "swimming". They are completely harmless and really interesting creatures. I call them fat, sad reindeers (well, they look like it :D).


Seed Shrimp, Ostracoda



Size: 0,1 - 0,2 cm, 0.04 - 0.1 inches

Seed shrimp are tiny seed shaped crustaceans. They are usually a bit bigger than Copepods. They move in a same fashion as Copepods, eating all kinds of nice things from the glass/plant/etc. surfaces and you can see them walking inside the substrate too. Sometimes they swim in open water looking like drunken bees. Here's a really young CRS baby looking at a seed shrimp. Really cute, harmless.

Freshwater Limpet - Acroloxus lacustris




Size: 0,1 - 0,8 cm ; 0.04 - 0.3 inches

Since freshwater limpets, Acroloxus lacustris, are so small and also move really slowly, it might be hard to identify them as snails. They are small and can't do much damage to plants, but since they are small, it's impossible to find and remove eggs and the baby snails. Harmless.

Something that looks a bit similar are Nerite eggs. They are singular, white, hard, round or oval shaped and about 1 - 2 mm in diameter.

Tubifex



Size: 2 - 5 cm, 3/4 - 2 inches

Red, yummy worms (used as fish food too) which live inside the substrate. If disturbed and dig up, they will form a ball, if left alone, they will gather pieces of sand/gravel around their body forming a sort of tube where they live in and they'll stick their head out of the substrate looking like red hairgrass. If there's lots of them, the substrate is too dirty and might be good idea to do something about it. Only a few Tubifex in the substrate isn't anything to worry about though. They are harmless.

Nematodes
Size: 0,1 - 0,3 cm, max. 0.1 inches

Nematodes are small, thin, white/transparent free-living roundworms and the "swim" moving themselves in a wave like pattern (well, forming an S shape). If disturbed, they will swim around wriggling briskly. You can find them from the substrate and they are the ones that might appear from the filter when you turn it on. These ones are harmless, but as with any other "pest", if there's too many of them, you are either overfeeding or just not keeping the tank clean enough of debris, decaying plant matter.

Planaria, flatworms



Size: 0,3 - 1 cm, 0.1 - 3/8 inches

Non-parasitic flatworms. Crossed-eyed grossness, just pure yucky! The only small creature I dislike (I get shivers down my spine even thinking about them). If you split it, it will regenerate and you will end up having 2 planaria. There seems to be several different colours in the common ones found in aquariums, transparent, white, brown and red. There's actually nothing really horrible about them, but they can bother small shrimp and snails and might eat fish/snail eggs.

They love shrimp pellets, pieces of meat, dead fish/shrimp and they will also eat small live creatures if they can catch them. They move on the surfaces, even under the water surface and are most active by night. If disturbed, they will retract themselves (shorter and wider), let go and drop down to the bottom.

Hydra



Size: 0,3 - 1,5 cm, 0.1 - 1/2 inches

Hydra are beautiful, but a wee bit annoying creatures. They spend their life attached to surfaces (plants, glass, filter, decoration), they can move a bit, but usually don't have the need to do that. If disturbed, they will retract their tentacles and body to small buds. They catch small creatures (copepods, Daphnia etc.) with their tentacles which can sting, making it easier for them to haul the pray in to their mouth opening. They pose no threat to adult fish, shrimp or snails (might cause some irritation if they touch the Hydra), but newborn fish and shrimp fry are in danger.

The species in the picture is Hydra viridissima and the green color comes from algae living inside the hydra.

Bryozoa, moss animals



Size: individual creatures are only a few millimetres long, the colony can be tens of centimetres long

Bryozoans are interesting colonial creatures. They look a bit like corals with the hard skeleton structure of the colony. The individual creatures, zooids, are inside their own small part of the colony and they eat small particles (phytoplankton, zooplankton) floating in the water by guiding them (and water) towards their mouth opening with the fan like tentacles. If disturbed, the zooids will retract their tentacles inside the colony walls. They are harmless and really interesting.

Springtails, Collembola



Size: 0,1 - 0,3 cm, 0.04 - 0.1 inches

Springtails are cool hexapods. They are used as live food for fish that eat from the surface, for example small Betta species and labyrinth fishes. You can find them more often from soil or leaf litter than from the water surface, but once in a while they will appear on the floating aquarium plants. If disturbed, they will spring to safety releasing their "spring" (furcula) that's normally bent under their body. They can jump surprisingly far (several centimeters). Harmless and cute.

Mosquito larvae




Text coming later.

Bloodworms



Text coming later
 
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#153 ·
i an a newbie and recently posted a trhead for biodiversity in an 8 yr old tank. i have seen all of these but most have bloomed and went collectively. great pics!! if you have any other recommendations please post. and a. hill i just got moss from you, i hope it come with the free hitchikers (minus the leeches). ill try to post some pics of my own miro-organisms but my camera isnt near as good. thanks for the info on that too!!
 
#154 ·
I had these in my tank...

now they look like these (at center).


I think they're hydra because now they have tentacles. Thought it might be helpful to see what they look like before they open up. I think the first one are the polyps before they open. Could they be other things?
 
#155 ·
The critter in the last pic is most definitely a shrimp, not a Hydra. (Unless you're talking about the really really really hard to see white filaments attached to the plant, in which case, they could be hydra, but it's really hard to tell without a higher magnification.
 
#159 ·
I can see that. It does look like a little colony of bryozoans more so than hydra. I went to http://www.planetinverts.com/what_is_that_bug_in_my_aquarium.html and it mentions for both hydra and bryzoans that they retract into themselves when disturbed. They don't move at all. Maybe i just have a lazy variety.

Also, from http://naturalaquariums.com/plantedtank/0807.html says "Very large colonies that look like giant egg masses are found in some lakes....Colonies not only will grow but sometimes zooids will produce statoblasts, an asexual form of reproduction. Statoblasts, are somewhat similar to seeds in plants." Maybe the first pic with the bubble things are statoblasts that hold tons of tiny bryozoans? Wish i would've taken invert zoology now..i really missed out.
 
#160 ·
That first blob tipped me off. I've never seen pics of bryos like that, but have seen enough to know they come in all shapes and sizes. Have never seen hydra morph like that, and personally have never seen them group together or colonize in fresh water, only with colonial hydroids in reef tanks. I consider you lucky, because I've been watching and waiting for bryozoa for a long time but still haven't seen any in my tanks.
 
#207 ·
Arghhhh i just found one in my tank. Guess he hitched a ride with a plant... Will they multiply ? Do i need to set off a mini nuke in my tank? What to doooooooo

Btw the one i saw i killed with my finger in the tank... :angryfire:angryfire
 
#174 ·
Not sure if this should go somewhere else so tell me if I'm in the wrong place (maybe should go in shrimp and other inverts?).

I have some strange little snails in 2.5 gallon of mine and was wondering if they do harm to plants. I've been googling around to try and find the species and the best i can come up with is they are in the ramshorn family (their shell is spiral and all on one plane). Though I'm not sure if I'm using the identification marks right.

Anywho, anybody seen this snail before?


It's like a ramhorn shell but sideways. They are only about 3-4 cm large. Sorry about the picture. It's the best I can do with my lens.
 
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