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Please help me identify this 1-2 mm nearly transparent animal which I found in my salt water aquarium.

  • $\begingroup$ Can you give some kind of indication of size, is it a freshwater or salt aquarium? $\endgroup$ Commented Sep 29, 2021 at 6:45
  • $\begingroup$ Can you say also if it's moving or not, is there any sign of a rudimentary (presumably transparent) shell? (I'm thinking freshwater limpet, but the symmetry may not be right). $\endgroup$ Commented Sep 29, 2021 at 6:59
  • $\begingroup$ Hi.. It may be in 1 Or 2 mm and i just 2days back only bought the aquarium and filled with salted tap water.. It's moving and it's walking with it's legs by walls only. $\endgroup$ Commented Sep 29, 2021 at 9:55
  • $\begingroup$ It's very transparent like water.. $\endgroup$ Commented Sep 29, 2021 at 9:56
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    $\begingroup$ with a good picture i could tell you what it is right now,please take a better picture by turning off the light in the room so only the water in the tank is lit and be sure to focus the camera properly. $\endgroup$ Commented Sep 29, 2021 at 16:08

1 Answer 1


Now THAT is a fish louse in the Argulidae family. They are bloodsucking parasites that attach themselves to fish with those round suckers near their head and feed with needle-like mouthparts. Needless to say, I'd advise you to find and eliminate as many as you can, as they'll be harming your fish with their bites.

  • $\begingroup$ Time to him read on all the fish parasites that affect common goldfish and tropical fish and see what to be wary of. $\endgroup$ Commented Oct 4, 2023 at 11:53

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