Aquaponics, upside down.
Fish feed plants. Plants take up what fish leave behind. Every aquaponic system is that loop. The Bubble just runs it at the bottom of the tank.
Air goes in. Water goes down.
Air in
Your aquarium air pump sends a slow stream of air into the dome. The air collects under the dome and pushes the water in the gravel down.
Roots breathe
The water drops below the gravel. For a while the roots sit in damp air, which is what roots want.
Water returns
When the air reaches the reverse bell siphon in the base, the siphon trips and lets it all out in one breath. Tank water rises back into the gravel and stops there: it wets the roots and never reaches the leaves. Then it starts again.
The part that decides.
In a normal grow bed, a bell siphon waits for the water to rise to a set height, then drains the whole bed at once. No timer, no valve. Just a pipe under a cap.
The Bubble's siphon is that idea turned over. It waits for the air to reach a set depth, then lets the air out at once. The water rises back into the gravel to take its place, and the wait starts again.
Why fish and plants get along.
Fish produce waste. Bacteria living on the gravel turn that waste into nitrate, which is plant food. Roots take it up, and the water that goes back to the fish has less of it.
And because the leaves are in air, the plant gives nothing up at night. Underwater plants take oxygen back out of the water in the dark. This one doesn't, and the air that drives it keeps stirring the surface the whole time.
One small plant won't replace your filter or your water changes. It is a garden first. But it is a garden that is part of the tank instead of sitting next to it.
Four steps, then leave it alone.
Fill the bed
Rinse the gravel and fill the gravel bed in the base.
Plant it
Sow seeds on the gravel or tuck in a small seedling or cutting.
Sink it
Press the dome on and lower The Bubble to the floor of the tank.
Give it air
Connect your airline to the port on the base and turn the air down to a slow, steady stream.