While I wrote recently about how clear the rainwater is in the washed gravel and sand areas and in the areas overgrown with Thai morning glory, the central part of the pond has just turned a bright green due to algae in the last few days.

Based on what I have read, algae needs two things to thrive: nutrients in the water and sunlight. The morning glory blocks the sunlight from reaching down to the water below and eats up the nutrients, leaving the water underneath quite clear. The rainwater that falls onto the washed gravel and sand has no nutrients for algae to use for growth.

But in the main pond area, there are probably nutrients leaching into the water from the (unlined) bottom and sides of the pond.

But why turn green all of a sudden now? My theory is sunlight. The rainy season is right now coming to an end, and we are seeing some very sunny days.

Interestingly, the morning glory is starting to grow out into the water from the edges in this part of the pond also, and I think I will let it continue to do so for now. I can always clear it out later.

In the next few weeks, I will get a more permanent electrical wire out to the pumps, so I can leave them on most of the day. Hopefully this will get the natural filtration process going and will help to filter both the algae and the nutrients feeding it out from the water.