One year it's cloudy, next year it's clear! What changed?

[Maddie Hopper]

Last year at this time the big pond was pea soup green with floating algae. It was so bad we emptied it, and I let it fill naturally when the rains came.
This year I can see the bottom of the pond, and there's no floating algae! Also, there are three small ponds in the stream that leads to the big pond by way of
a pond pump, however I have not turned on the pump this year because of the differences in the ponds' clarity. Each of the three ponds has different clarity. The first one is pea soup green, the second one is crystal clear and the third one is somewhere in between. What accounts for these differences?? I haven't turned on the pump in the event the first pond's algae would spread into the big pond and turn it green. I'm going to start putting Aquascape Beneficial Bacteria concentrate into the first pond.

 

[Lisak1]

Algae results from an accumulation of excess waste. If you don't have fish then I'd guess decaying organic material. Draining it may have gotten rid of whatever was feeding the algae.

How big are these ponds? Some people swear by bacteria in a bottle, but I wouldn't waste the money. Bacterial occurs naturally in your pond as it matures.

 

[poconojoe]

You need to determine the difference between all three ponds.
We can't diagnose it from a distance without more information.
Something has to be different.

The green pond likely has much more excess nutrients than the other ponds.
The algae is nature's way of balancing the pond's ecosystem. If nature didn't perform this failsafe, your fish would probably die.
So, the algae isn't bad, it's just nature's way of correcting the imbalance since you don't have enough plants to do it. The fish don't mind it nor is it bad for them. We just like clear water so we can see our fish. Ponds and lakes in the wild are not crystal clear.

Is it possible the green pond has had any ground runoff? IE: fertilizer getting into the water? Any fertilizer will enhance algae growth.

How many gallons do each pond hold?

Does each pond have fish?
What kind of fish?
What size fish?
Does the green pond have a larger fish load?

What type of filtration do you have?
Do the ponds share the filter or does each have it's own?
If they share the filter, where is it located?

Do you have any aeration? Even just breaking the surface tension is helpful.

Do you have any plants in the ponds? Without lots of plants you are missing a piece of the natural puzzle and will have green water for sure.
Toss some floating plants in there. They help filter the water and give shade from the sun. No pots or planting, just toss them in.

Are all the ponds recieving the same amount of sunlight? Maybe the one that's green is getting a lot of full sun?

Have you slowly netted out any accumulated debris from the bottom of each pond?

Don't waste your money on store bought bacteria. You ponds produce the bacteria on their own.

Don't add ANY chemicals to combat the algae, you will kill any fish you might have. No algecide, "pond bombs" or any other wallet emptying snake oils.
The safe and natural way to get rid of algae is to add lots of plants to compete with the algae.

Don't clean your filter with chlorinated water. The chlorine will kill the beneficial bacteria colony. Use pond water.