金魚茜(Ceratophyllum demersum)
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Ceratophyllum demersum is a genuine cosmopolitan found all over the globe. It has no true roots but can be planted in the bottom. In the wild it is often found rooted, with the lower leaves forming anchors. As a floating plant it provides a good hiding-place for young fish.

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C. demersum can be useful in combating algae because it consumes nutrients in the water and secretes substances that counteract algae. <-

Some varieties are difficult to transport