Eutrophication is when the phytoplankton population explodes and depletes all the oxygen and kill all or most of the animals.
This happens when nitrogen and phosphorus nutrients build up and cause the algae to bloom.
The ecology in Experiment Tank #6 crashed from Eutrophic Collapse.
How did it get overwhelmed with nitrogen and phosphorus?
Because so many frogs laid so many clutches of eggs in it. Clutch after clutch.
It is the tank closest to the adjacent shrubs.
It was the preferred rendezvous for the Green Frogs, and may have been the same for the Gray Tree Frogs.
I think I saw frogs copulating in it every 2nd or 3rd night for a few weeks.
Anyway, I had already renamed Experiment Tank #6 as “The Grossest Hot Tub in Vegas” because it saw so much action.
I was still surprised to see that the secretions from mass amphibian sexual activity could overwhelm the ecology of a puddle.
It shouldn’t be surprising, but I think it is merely because of how gross it all is.
Remediation
There were some surviving tadpoles and mosquitofish, but I think many tadpoles probably suffocated and contributed to the collapse.
All elodea appeared to be dead, and most had decayed.
I let the water hyacinth grow and remove some of the excess nutrients.
Then I removed some of the water hyacinth and added some new elodea from other tanks.
Here is what the water quality looks like in a more healthy tank:
Notice how clear the water is when the macrophytes (water plants) are doing a good job tying up available nutrients:
