FAQs on Aquatic Insects and Freshwater
Invertebrates in Freshwater Aquariums,
Invertebrates for Freshwater
Aquariums by Neale Monks,
FAQs on Aquatic Insects:
Aquatic Insects 1,
Aquatic Insects 2,
Aquatic Insects 3,
Aquatic Insects 4,
Insect Identification, Aquatic
FAQs on Aquatic Insects by Group:
Flies in General (Caddis, Gnats, Midges...),
Freshwater Mites, Mosquitos/Mozzies and much more!
Hello my name is Mehrr, and I've found these work like creatures in my
fresh water tank. Could you please tell me what they are?
<Are these in your aquarium? Seems odd. These are maggots of some sort -- larvae
of flies (i.e., Diptera) -- perhaps houseflies or blowflies.
Harmless, and most big fish will eat them very readily. They do not live
underwater though, so more likely have fallen into the aquarium from above.
No, they were in my fresh water tank.
<Oh, I'm sorry, I'll issue a refund at once!>
It's a giant covered, concrete cylindrical structure used to store fresh water
for domestic purposes.
<Not really what the volunteers here are expert in.>
Are they commonly found in such an environment?
<Maggots are terrestrial and must breathe air, but do prefer dark, damp
environments with plenty of decaying organic material. Trash cans, compost
heaps, rotting food are the sorts of environments they favour. Examine
where this tank is located and act accordingly. There are aquatic maggot-like
animals of course, such as Rat-tailed maggots, that do live in swampy, polluted
ponds and ditches, but they are very different in appearance to traditional Blow
fly, House fly, and similar maggots. Cheers, Neale.>
Worms in my tub! 5/3/17
Hello! Can you please tell me what kind of worms these are?
I found them in my bathtub after giving the kids a bath! We live in
northwest Indiana if that helps any.
<These look like insect larvae; likely hatched from "flies" getting into
the house, some bit of water left in the tub... no worries. Bob Fenner>
Worm, Larvae, or other?
Just finished cycling a Fluval Edge 6 gallon aquarium after 4 weeks. I
cycled with pure ammonia from Dr. Tim's Aquatics dosing 4ppm each day the
ammonia read 0ppm. The tank is planted with Helianthus callitrichoides,
Lilaeopsis brasiliensis, Vesicularia dubyana, and a few Aegagropila
linnaei. I dose with Flourish Comprehensive weekly and Fluorish Excel
daily with 12h/day lightning by means of my Finnex Planted+. The plants
growing wonderfully. There are also some snails that hitched a ride on
the Java Moss
I purchased from my LFS
, which I don't mind at the moment.
I have yet to perform a water change
and will do so after I figure out what these pests are. First here are
the water specs to get an idea of the conditions:
NH3, NO2 0ppm
NO3 80ppm (as I said, have yet to do a water change
<Who? The worms I'll assume.>
have definitely proliferated in the past few days (probably due to
increased nitrate concentration), with most coming out at night and
wiggling erratically at the top of the tank. Few also float in the water
column during the day. The majority are translucent with some varying
with brown specks. The supposed worms appear to be segmented, which
leads me to believe they are of the Annelid phylum or are larvae of some
and therefore not Planaria, but then again I could just be seeing
Maybe they are some sort of Dipteran larvae?
<Can you send along a well-resolved pic? The two groups of
invertebrates can be discerned on close inspection>
Please let me know!
<Please read here re identifying these groups:
Re: Worm, Larvae, or other?
Oh yes! The most important part of the email was omitted! Here is a
<Ahh; these appear to be insect larvae. I'd vacuum the gravel to remove
them. Bob Fenner>
Re: Worm, Larvae, or other?
Thanks for the help IDing them! I am planning on getting a school of 6
cardinal tetras, so I hope they will find them to be a delicious treat.
<Which? I'd remove the larvae as stated... They may turn out to be fish
eaters, or flying about your house... BobF>
Nematode worms 6/19/15
Dear WWM crew,
I happened upon your site following several searches to try and identify the
worm-like creatures I found on the bottom of my outdoor swimming pool.
I realize your site is for aquarium enthusiasts, but your specialists seem
really knowledgeable about worms and larvae, unlike most of the drivel I find in
"Yahoo Answer-like" web postings. Could you help identify the fast wriggling
creatures in the attached video, <insect
pool larv.mov> and recommend how I can get rid of them? They inhabit a 100ft
long outdoor swimming pool for recreational swimming and most users would
probably not like to share their swimming enjoyment with these creatures.
Thank you for your expertise!
Marc de Beer
<There isn't enough detail to say what sort of "worms" these are, whether
annelids, nematodes, Nematomorpha or insect larvae. Nematomorphs are pretty
common though, and generally harmless to us since they infect different sorts of
animals. Unfortunately, chlorine levels in pools are not normally high enough to
kill the durable eggs of some "worms", and insect larvae may appear repeatedly
because the flies, mosquitoes and other species can come to a clean pool and lay
their eggs there. In short, there isn't a one-shot chemical solution to these.
Net them out, and in particular, remove potential hosts as quickly as you can to
prevent possible reinfection -- typical hosts for Nematomorpha are insects
including flies, crickets,
beetles and so on. Cheers, Neale.>
<From the motion of the animal in your MOV, am pretty sure this/these are insect
larva/e... See WWM re. Bob Fenner>
Re: Nematode worms 6/20/15
Thank you so much!
<Simple chlorine shocking procedure will very likely rid your system of these
larval insects. BobF>
What is this? 5/30/15
I have put an avocado pit in water and after a few weeks, I found these worms in
the water. The most pointy side are mostly at the top of the water, as if for
<Can't really tell from your photo but description matches "rat-tailed maggots"
which are the larval form of specific types of fly and very interesting beasts!
Not many people get to see them, so well done! Probably better outdoors in some
swampy bit of pond though. Cheers, Neale.>
Strange worms in tubes and algae
I have a newly planted freshwater aquarium with no fish. I have a few Amazon
swords, crypts, and Anubias plants. I have 2 t5 fluorescent grow lights. My
planted tanks has some kind of dark green algae with squiggly lines and with
some kind of worms. The worms are growing in some kind of single tube.
<Indeed! Sessile chironomid larvae or similar. Also an Hydra visible in one
photo, the branched, off-white tree-like organism.>
The worms poke their heads out of tube for a few seconds and then go back in the
tube and hide.
I can't find anything like them on the internet and was hoping you might be able
to tell me what they are and if I should get rid of them and is it safe to put
fish in the tank with them?
<Harmless filter-feeders; fish food. The hydra is a bit more of a risk in a
breeding tank (will catch, eat tiny fry).>
Here is a couple of pictures. Thanks in advance for any help you can provide.
<Most welcome. Neale.>
very nice pic.
Re: Strange worms in tubes and algae
Thank you so much!
<Glad to help. Neale.>
Wormlike wigglers in cycling tank
Can you guys identify what these are? They appear to be little white
worms in the water but zoomed in they look like larvae of some type.
This is in a new setup about 4 weeks old, no fish, fresh black onyx
sand, RO water, and 81 degree temp. They seem to have come out of no
where. Thanks in advance. Video below image.
<Midge larvae or something similar. Totally harmless, and likely fish
food if you add anything insectivorous of appropriate size (such as
tetras). Not mosquitoes, anyway, which attach to the surface film of
water. Cheers, Neale.>
Wormlike wigglers in cycling tank /RMF
Can you guys identify what these are?
They appear to be little white worms in the water but zoomed in they
look like larvae of some type. This is in a new setup about 4 weeks old,
no fish, fresh black onyx sand, RO water, and 81 degree temp. They seem
to have come out of no where. Thanks in advance. Video below image.
<Insect larvae... heads appear too small to be mosquitoes, maybe Midge
larvae. I'd net out, remove. Bob Fenner>
Re: Wormlike wigglers in cycling tank
Thanks for the reply. I added what is now a very full and satisfied
Platy to the tank.
<Heeee! I bet!>
The thing couldn't get to the little morsels fast enough. Happy to say
that all wigglers are gone.
<Cheers Mark. BobF>
Could you all please I.D.
Any clue? I've asked around, yet nobody seems to know.
<Mmm; would like a bigger, better resolved pic... My initial guess is
that this is a juvenile Tunicate, a larval
Ascidian of some kind/species.
Re: Could you all please I.D.
This is the best I have
I had gotten rid of him, I didn't want him to harm my tank.
Thanks for getting back with me bob Fenner
<My guess is still on the Thaliacean. BobF>
Inputs for Bob (Re:
Could you all please ID dated 1/1/2015)
To my Kumpadre Bob,
Hi! I hope you and the crew had a great time during the holidays. I'd like to
chime in on the erstwhile unidentified organism in the letter dated 1/1/2015. No
info was given regarding the habitat, but if it was collected in freshwater, it
might be a rat-tailed maggot.
<Just looked up; neat!>
I had fun collecting these in anoxic creeks during my younger years in Manila
(gosh the memories ha-ha). Hope this info helps. Thanks for all the help you and
the crew have been providing all these years, and wishing you all the best for
<Mabuhay mi pare jo! Bob Fenner>
Weird Things in my Tank 11/6/14
Hello, my name is Brooke. I'm writing in regards to these strange
I found in my boyfriend's fish tank. He has a 29 gallon tank that was
purchased on September 27th. He currently has 3 Gold Danios and a
couple snails. He's waiting for the tank to
cycle before adding other fish. The PH is
about 7.2. The ammonia fluctuates between 0 and 0.25, the Nitrites are 0
and the Nitrates are at 40. He's new to the hobby, but has done
everything according to what the people at our
local fish store have recommended. He keeps
the tank at 76 degrees. He has an Aquaclear 30 filter. He has live
plants that were purchased at the time of the tank, before the
fish. He has, I believe, Fluorite Black
substrate mixed with a little black gravel.
We do weekly 10% water changes. During the water change, he suctions the
substrate as well as he can without digging up plants. I'm not
sure if all of this is useful to you in
helping to ID these creatures, but figured it
would be better to include it, just in case. I noticed the creatures
about a week ago. They looked like small bits
of root coming off some of the plants that
have been floating at the top of the water. The creatures were
green in color, small, and long. After closer inspection, I saw
that there were also some that were a little
larger and brown. I did some research (days of
pouring over Google as well as your site) and couldn't find
anything other than maybe a Damselfly Nymph, but still felt like
it was unlikely. I decided to watch and see
what happened. As they got larger, they
started to look like they had little bug or shrimp bodies sticking out
of the long, skinny, brown "shell," and I could see a "vein"
pumping through the "shell." They also look
like they have a long piece of plant root
attached to their top sides. They don't seem to have a preference as
to which portion of the tank they are in, as long as they are on
I've seen them on plants at the top, walking on the walls, and walking
along on the bottom of the tank. Although, they do seem to like
being on the plants the most. I tried to get a
few pictures of them, though it's
hard as the biggest are only about an inch in length. I'm including a
picture of a smaller one as well as a close up of a larger one
from the top and a larger one from the side.
My main questions are: What are they? Are
they safe to keep? If not, what should I do?
If they are, is there anything
I need to know about their care? I've found them quite
interesting to watch, so I'm hoping they are
keepers. Thank you so much!
<The photos aren't sharp, so can't be sure. But are these Caddisfly
Larvae or something similar? That's what they look like to me. They're
hugely diverse, including some species that eat algae, some that feed on
particles of organic matter, some that capture small invertebrates such
as other insect larvae. I can't think of any that eat fish, and they're
so small none should be a threat to anything bigger than, say, fish fry
anyway. So you might want to observe this beast a while longer. Look up
Trichoptera in your local area and see if any match the animal you have
here. Cheers, Neale.>
Re: Weird Things in my Tank 11/6/14
Thank you so much! It looks like that is exactly what we have. I suppose
we'll watch them, and once they have emerged from the water, we'll
catch them and let them go outside. They're really
quite fascinating! It's hard to believe they've
built their cases out of stuff they've found in the tank!
I really appreciate all your help as well as your quick reply!
little worm in freshwater tank
Good evening! I would like to ask your help identifying a worm I found
yesterday. While cleaning out my tank, I noticed some little, very light
colored worms on my Anubias nana. I put them in a bowl for observation.
They didn't climb on the wall, just wiggled on the bottom. I haven't
seen them in my tank before, though they are small and my gravel is
light so I might have missed them. There were only a few. The body is
round, so I think it's not a flat worm, there was also some black
coloration on the head. I inspected the leaves and I found some brown
round things on one of the leaves, maybe the eggs or something? I took
some pics with my phone but they aren't the best, I don't have a camera
so I can't really make better ones, sorry. My questions are what is it,
is it harmful to my fish, do I need any treatment for the tank? My
friend suggested that I throw away my plants, but I don't really want to
if it's not necessary. I live in Europe.
<Likely these are aquatic insect larvae, possibly imported on the
plants, and in any event, almost certainly harmless. Nematodes
(roundworms) tend to be uniformly coloured (usually white) whereas
insect larvae (such as "maggots") have distinctive head regions that are
darker than the body thanks to their eyes and jaws. Hope this helps,
Re: little worm in freshwater tank
Thank you for your reply, I'm relieved. Than I go and replant my tank :)
<Most welcome, Neale.>
Worms of some sort, in turt sys. 12/11/13
I have a freshwater tank with 3 red eared sliders in it and I went and
vacuumed the water and then as I refilled the tank I saw some
red squiggly crazy freaking out worm with a type of pincher at the tail
end and a mouth that looked like it was unhinging
<... not an Oligochaete>
or somewhat snake like as it was eating the floating crap that I stirred
up when cleaning and refilling.. then I noticed with a closer look that
there are a bunch of way smaller worm like things swimming around in
there as well. These ones are harder to see because they are so small
but are doing the same thing the big red one does, as in squiggles
around completely looking like a crack head freaking out. Will these
things hurt my turtles? I've attached a video of this crack head worm..
<Mmm, from your description these are likely some type of insect larvae
rather than worms... But the latter are a possibility as well (from live
foods, plants... see Darrel's rec. re "Koi" pellets as a standard
At any length, neither are harmful to turtles... Read here:
and the linked files above. Bob Fenner>