Aquaponics - auto top-up water

I've had an idea.

I had my duckweed tank connected to my fish tank via a no holes siphon (a tube full of water with en end submerged in each container). This saved the day when I had a spill from my strawberry tower.

The level in the fish tank and the level in the duckweed are always kept exactly the same, so if I add water to the duckweed tank, it flows into the fish tank, until equilibrium is reached. This means the duckweed tank breathes in and out with the fish tank.

That all works well, but I would prefer to have the duckweed tank full, to add extra thermal mass to the grow house and keep temperatures more stable.

So what I thought I'd do is make a flexible hose from the bottom the duckweed tank go over to the fish tank, but instead of submerging the end, I'll add a float, and a vertical pipe. If I cut the pipe at the same height as the duckweed tank water level when the float is floating in a full fish tank, I think water should flow from the duckweed tank into the fish tank if the water of the fish tank gets too low.

I think.

Or something.

Definitely something interesting or not should happen.

I'll try it.

If it works I'll explain it better.