That is a really elegant looking onion growing apparatus. Nice.

Whenever I've tried that I always end up with rot. How come you didn't? Is is just a trick of keeping the water at the right level?

Yeah I've had the same problems in the past, so this time I suspended the onion right above the water level so only the roots are in the water.

I tried that once but I had to keep refilling every few hours or it would evaporate and leave the roots dry. I just wasn't conscientious enough to keep it alive that way.

I wonder if one could devise a simple system to use a large reservoir to keep the water at a constant level?

The only problem with that is the larger the reservoir the more surface area, which means more evaporation. If you had a something that tapered so that it was very wide in the middle and then narrow at the top it would probably work better.

I was thinking a little bit more complex than just an open reservoir. Like a pump to keep the beaker full, with an overflow port too keep it from overfilling. It's hard to describe so here's a sketch:



The downside is you'd have to have a pump running, but it wouldn't have to run all the time (just once every few hours) and the drip action might even take the place of the air bubbler.

I built a very similar thing when living at Valencia to water my venus fly traps. The best way to water them was to keep about a CM of water on the bottom of a tray, but you can imagine it would be hard to keep that at a constant level. Pretty much an EBB and FLOW system that is continously going. I'll update this post later with a picture....

Another way to do it would be to put the reservoir above the level of the beaker, and connect them with a valve that opens when the water falls below a set level and closes when the water rises back up. Kind of like the one in your toilet tank (assuming they work the same way in Australia).

It just seems like there should be a way to do it more simply, without a pump or a valve, using a siphon or something. Or maybe not.

Anyway post those pictures of your flytrap apparatus.

Flickr Set

Cool system. Those look like healthy flytraps!

There are lots of people doing this for fish tanks (especially saltwater reef tanks), they call them Automatic Top Off systems (ATO's). Here's a DIY youtube video of some guy making one:

I didn't know you could get a premade float switch like that. Awesome!

But as for his technique: please just spend the three bucks to get a project box and a couple of wire nuts at Radioshack so you don't set your house on fire.

Also I just kept waiting for him to slice his thumb open with that razor blade.

I don't have that problem here...maybe because it is so cold. Refilled it for the first time today on day 8.