I want to know the term in English for the green slippery substance formed on things that are standing in water. I can only think of "algae" or preferably "green algae"; these are in the context of science.

But is there any other general word in English used for this green slippery thing? In Hindi we say, Kaayi, so what is Kaayi in English?


4 Answers 4


A generic word is slime: Slime algae on backyard ponds. This could occur on the surface or on the side of tanks.

slime noun

2. a. A viscous substance or fluid of animal or vegetable origin
(in this sense: 13th century)


  • Depending on your audience, slime may have a connotation of a slime mold which is a completely different organism more closely related to fungi (like mold) than plants. Okay, only pedantic biologists would like point this out, but it's worth noting for how confusing English can be.
    – Patrick M
    Commented Jan 10, 2014 at 21:57

The closest English word I can think of is "scum" (but "pond scum" completely matches your definition);

scum n. a layer of dirt or froth on the surface of a liquid.

pond scum n. Any of various freshwater algae that form a usually greenish film on the surface of stagnant water.

  • 1
    Pond scum is free floating while kaee is not. It is usually on the sides, like the walls of a tank. Commented Jan 10, 2014 at 14:32
  • @Preetie Scum does not need to be free-floating. Scum: 1.c. a slimy film on a solid or gelatinous object
    – Kit Z. Fox
    Commented Jan 10, 2014 at 14:44
  • 1
    @PreetieSekhon Informally, we might call that scum on the sides of the fish tank. My friends with aquariums call that a bloom. Commented Jan 10, 2014 at 14:46
  • 2
    @ElliottFrisch Or more generally gunk. Commented Jan 10, 2014 at 18:16
  • 1
    scum from a Biology text. 4.6 Sludge, Supernatent, Scum, and Sand and here. Commented Jan 10, 2014 at 21:35

Here in Madison, Wisconsin, we use the scientific term, Algae. People call it Lake Algae because Madison is situated on 4 lakes and that is where it forms and is often observed.

Lake Algae article


This could also be (an underwater variety of) moss.


moss NOUN

1 [MASS NOUN] A small flowerless green plant which lacks true roots, growing in low carpets or rounded cushions in damp habitats and reproducing by means of spores released from stalked capsules:

the trees are overgrown with vines and moss

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