Random Bits: Elodea Self Sustainable Aquarium Study

Starting from March 2018, I've been testing Elodea for self sustaining aquariums with fish.

Initially, I grew Elodea in plastic bottles and later moved on to testing Elodea in 3 liter glass jars as shown in previous videos.

Elodea is one of the fastest growing aquarium plants that can double and triple size in a month.

And my dwarf guppies eat Elodea.

It makes Elodea the second candidate for self-sustaining aquariums that I decide to check on.
Filamentous algae was the first and it failed ;)

But let's get back to Elodea.

I noticed that something weird happens in aquariums with Elodea as the plant takes over all available space.

Common green algae starts blooming.

It happens while light, feeding, and temperature in the aquarium remain the same.

I decide to put Elodea under observation into a smaller nursery where it should take less time for Elodea to fill up the space.
A disposable plastic cup will do for this purpose.

Fill it up with dechlorinated water.

Add 6 cm long cutting of Elodea.

Cover the cup with a planter to reduce water evaporation.

And let's add seed shrimp.
Seed shrimp feed on algae and organic detritus making them the perfect cleaning crew for aquariums.

I expect Elodea to grow quickly, taking all available space in this small nursery.
A gang of seed shrimp feeding on algae should provide enough waste for the plant to grow on.

I place the nursery on a windowsill on August 4th, 2019.

Three weeks later, on August 21st.
The Elodea plant did not grow at all.

The plant seems to be dying.

The water is greenish, indicating on algae building up.

Well, let's setup two more nurseries in cups to check the results.
This time, I set up nurseries the way I usually set up all my aquariums.

Add gravel, rocks, seashells, dechlorinated water.

Add slow growing Marimo ball and hairgrass.

And here come Elodea cuttings.

Add seed shrimp.

Cover both nurseries to reduce water evaporation.
The atmosphere air flows in and out through tubes in covers.

I add pond snails in one nursery and ramshorn snails go into the other.

Snails feeding on algae in addition to seed shrimp should provide much more waste for plants to feed on than seed shrimp produce alone.

Both new nurseries are ready on September 25th, 2019

I place them on a windowsill, next to the first nursery.

It's been less than 2 months since I set up the first nursery.
The water in the first nursery is clear - seed shrimp have been taking good care of algae.

The biggest part of this Elodea plant is dead.
The remains of the plant seem to be dormant.

Here, you can see the two Elodea plants about four months later, on January 16th, 2020
Once again, Elodea plants did not grow.

Some parts died and remaining alive parts seem to be dormant.

As a result, algae has been growing.

Tests in 3 liter tanks yields similar results as soon as Elodea grows to the capacity of the tank.
Here you can see a nursery with Elodea already growing above water level on January 16, 2020

There are no signs of algae in this aquarium yet.

Elodea reduced the growth pace shortly after that and went dormant, allowing green algae to bloom as you can see it even 3 months later on April 26th.

The bloom of algae happens after fast growing Elodea stops growing like in these two aquariums - stops consuming nutrition, and wilts making nutrition for algae to grow on.