This is an easily available attachment for pop bottles here in Canada. They are available in garden centers for watering plants.  This means the the entire windowfarm can be made from pop bottles and still get excellent airlift.

Your water tube would go down in a J shape to the t- joint to prevent back flow into the reservoir.

If you cut the “showerhead” top off, you can use an upturned pop bottle as your reservoir for a windowfarm and  attach the water pipe to a t-joint  outside  the bottle  and at whatever submergence you choose.  I think this can make life easier for everyone.

Plant watering attachment for pop bottles