Thanks for your suggestions and comments, everybody. I hastily made my reservoirs darker, but will have to address the issue more thoroughly in a near future. I used thick cardboard to make a niche for my upper reservoir and poster cardboard to cap the bottom one. Look at the photos. Wouldn’t it be wise to cover the tubing as well, inside a sleeve of black fabric, for instance ?
I’m still looking into a sustainable pumpless system. I figure that I can live with the chore of climbing up once every three days to refill my upper reservoir. But I’d like to refine the design. And I thought about capillarity, this capacity of a spongy material to sip water up to a higher level. Still juggling with the idea. I have the habit to leave my plants at school with a very simple but very effective capillarity system to water them during Christmas vacations. By the way, I enrolled my younger daughter in this thinking process.
Meanwhile, I continued my experiments with the slow drip, utilizing the 600mL container, since I like the idea of suspending it directly above the plants. I doubled a simple string of unknown (synthetic) material, made a knot to tie its two ends together and squeezed the fold up into the silicone tubing. To my surprise, this slowed the flow very significantly. (In my first attempt, using the enteral tubing with the slow drip system built in, the bottle was empty after 3 hours.) This last system lasted 84 hours (3 days and a half) during which it needed no intervention from my part.
But I think I might have been too successful in slowing the whole thing. I’m afraid the plants wouldn’t receive enough water. So, I thought of coupling two 600mL bottles side by side, and join the two strings together to double the volume of water, which I’ll try out no later than tonight.
Which brings me to my question : does any of you out there can tell me approximately how much water you need to put through your system over a period of 24 hours to sustain your plants’ needs ? What would be your estimate ? And did I understand correctly when I read that people put their air pump on a timer to make it work only 15 minutes at a time ?
Last thing : Somebody gave me 2 swivel curtain rods, a few years ago, which I kept intending to use them for another project. I stumbled on them by chance while looking for something else. And I think they are just perfect for what I have in mind. I want to be able to get the whole window farm to get out of the way when I want to access my window. These rods move just like window shutters and their tubing is square, so we think that they would be strong enough to sustain the weight. I’m posting a photo and will certainly try them. Only need to figure out a way to stabilize the different columns of bottles at the bottom, possibly by tying them to a wooden rod suspended underneath the last row of bottles.