I designed this watering ring to fit around my bonsai tree. It has a coupling to fit the standard 4.3mm inner diameter aquarium air hose. The ring is oval shaped and is a 100mm by a 150mm. There are 14 holes equally spaced in the ring facing inwards. The holes have a diameter of 0.5mm which is a bit small, I had to drill the holes out afterwards which to me wasn't a problem.

I have included the solidworks part for those who want to edit it.

Happy gardening!