It is brown diatom algae. You can take them out and rinse them and then rub off the algae. I used to use a toothbrush (buy a cheap one just for aquarium purposes) to scrup off the algae. You don't have to remove it as its not harmful to fish...I just didn't like the way it looked.
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*Kristin*
5 Planted tanks:
55g, 40g, 29g, 10g, 5.5g
10g N. multifasciatus tank, 5.5g Platy fry
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