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Hi,

I have seen a few critters in my shrimp tank and I'm wondering if anyone can firstly identify them and secondly let me know if there is any harm in them being in the tank.

The tank set up if it helps is a 10 gallon which has been running for approx 4 weeks with regular aquarium gravel, small powerfilter, driftwood, java moss, vals, some leaf litter and a type of thread algae (the last two being supplied by the guy who supplied the shrimp as a food source and to help the shrimp settle in). The tank is unheated but sits at around 30C (86F) thanks to our tropical climate.

tank picture
leaf litter and algae

I currently have 9 ninja shrimp (Caridina serratirostris) in the tank, 4 of which are carrying eggs. There are also a couple of varieties of hitchiker snails that came in on the plants and on the leaf litter.

ninja shrimp
snail

The first critter I would like identified is wormlike, white to cream in colour with a black head. I initially thought planaria but it does not appear to have the spade shaped head of all the planaria pics I could find.
Photos linked below:

worm pic #1
worm pic #2
worm pic #3
worm pic #4 - incl measurement

The second critter that I would like identified is shown in the pic below. I was only able to get one semi-decent shot as it is really small (about 1mm) and seems to move pretty fast. The colour of these vary from white to green.

critter #2

Any input would be appreciated. Thanks for your help

G_T

Never be afraid to try something new. Remember that a lone amateur built the Ark. A large group of professionals built the Titanic.

The worm looks like a tiny midge or fly larvae, the other thing looks like a freshwater copepod, I dont know the exact species. Calilassea probably would though.

Does that bottom critter have any sign of a shell or legs? Pic isn't clear enough. If it's got a smooth body and any hard shell it's some type of snail. If it's got legs and no shell but what looks like a hard top then it's probably a copepod or something similar. Copepods kinda look like an aquatic version of the pill bug or rolly pollies. Whatever you call them in your area. If you do a google image search for copepods you'll see pictures of saltwater ones.

Your snail is a common pond snail/pest snail. Physidae species. It will multiply like crazy if you overfeed the tank at all but otherwise aren't harmful to shrimp breeding tanks. How much food they get directly affects how many snails you get so if you see too many your putting in alot more food than your shrimp can eat.

The worm is likely to require specialist determination. Pop it in a phial in 10% formalin and mail it to your nearest natural history museum for determination to species level.

The snail looks fairly interesting - probably Family Physidae as already mentioned above, but then you have the fun of determining its identity to a finer taxonomic granularity. Even genus determination with some of these can be problematic, and if this is a native American snail, you'll need some expert advice.

Your last critter is interesting. Was it swimming openly for long periods or did it swim only briefly before attaching itself to a solid object?

If it was swimming openly on a continual basis, chances are it's a copepod or a Daphnia like crustacean, possibly one of the Bosmina species. Mind you, this is another area where you'll need specialist advice if you want determination to species level. If the critter spends most of its time clinging to a solid object and roving around the surface of siad solid object, then it could be an Ostracod, but Ostracods usually have a much more bean-shaped shell, and visible swimming/walking appendages at both ends of the shell. If it was moving through the water with a noticeable vertical "hopping" motion then it's a Daphnia type creature, and probably one of the Bosmina species (which are usually fairly small).



Panda Catfish fan and keeper/breeder since Christmas 2002

The second critter is the same thing I've got in my 10g tank - it's an ostracod.

Listen! Do you smell that?

For those who are interested, here is your introduction to ostrcods page.

Note that this page goes into a fair degree of detail.


Panda Catfish fan and keeper/breeder since Christmas 2002

besides the snail,are any of those little critters mentioned above harmfull,to fish or fishtank water,and would they have hitched a lift on the plant,or the fish or the snail?

If you have fish living in that aquarium with the snails and they're showing no signs of disease, then you can presume that nothing pathogenic has been unleashed in there yet. And, with the passage of time, the probability that something will be unleashed in there that can be traced to your hitch hikers diminishes markedly.

The only time that snails are troublesome is when you're trying to spawn egglayers. Some snail species will consume fish eggs with undisguised enthusiasm (although you would have to look hard to see the look of glee on the snail's face!). Some tropical snails can harbour unpleasant hitch hikers of their own, which is why you don't see many tropical snails in the shops apart from a very few that are known NOT to carry such hitch hikers, and which have been bred in captivity and have therefore a guaranteed provenance in this regard. This is because some of the hitch hikers that can travel with snails are dangerous to humans. Schistosoma parasites are the classic case in point - there are numerous species of these, and ALL of them cause serious and life threatening disease in Man. Which is why you won't be seeing African snails from the shallows of Lake Victoria in the shops any time soon.

The worm-like creature you found will need professional determination as I stated above. If you want to see the kind of insect larvae that usually appear in ponds (and which differ very markedly form your "worm", do a Google image search on the following genera:

Chironomous
Chaoborus
Culex

The first of these is the familiar Bloodworn, the second an interesting creature called a Glassworm (which also makes fine fish food) and the last of course are midge/mosquito larvae (of which there are many more genera, but some of those again are carriers of significant human diseases, which is why there's a good chance you won't see them because of multi-million dollar mosquito eradication programmes).

Ostracods have been part of the biosphere's means of processing POM (Particulate Organic Matter) for aeons. Most are detritus feeders that will undergo a population explosion if you overfeed your fishes. And perform a useful sanitation service both in the aquarium and in natural ecosystems thanks to their detritivorous habits. It's actually amusing to watch some fishes try to eat these hard shelled crustaceans, as many of our aquarium fishes don't have the dentition for the task. Those that do, however (some Dwarf Cichlids will munch on them happily) will help themselves to tasty snacks and supplement their diet accordingly.


Panda Catfish fan and keeper/breeder since Christmas 2002