Why healthy plants can resist algae

tiger15

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Aug 12, 2017
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Terrestrial plants produce toxic sap or employ biological agents to deter insect bite. Fish produce body slime that is antiseptic. Only injured, sick and dying fish invite fungal and bacterial infection. What is your explanation on why healthy plants don’t get algae.
 

Phishless

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Jul 13, 2017
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Healthy plants that are growing well will not have rotting leaves or stems.
Damaged plant tissue is a great source of dissolved organics, great locally concentrated food source for algae.
When the plant tissue is soft during rotting snails dig in too, but they won't get it all.
Shading, lower leaf disintegration are all signs to trim and clean things up.

This is my stab at it!
 
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Paul G

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Sep 28, 2011
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Agree emphatically! I would add this: I have a really big swordplant that constantly produces leaves and runners. When the oldest, biggest leaves start to show their age, they are removed. They always have holes, yellowing dying tissue, and develop skins of various green algae, as well as BBA along their edges. The plant wants to be rid of senescent leaves. When trimmed up, and the plant is kept tidy, there is no algae to be seen. This is a clearly drawn example of the general idea, pointed out by Phishless, that older parts of plants can show "damage" from gradual changes in their immediate environment such as light deprivation, poor water circulation, etc, due to overgrowth and crowding, as when stem plants get long and leggy, with only the newest growth being healthy. It is not surprising to see the ugly dark algae being fostered by this.