Well I guess as the water goes down fresh air should enter, there's the pipe and a slit around all sides.. so yeah if it does that... okay well I still have airgap, so what I should have said I'm not believing the airgap holes are necessary? although they might airprune the roots which might be beneficial
When I designed my Triforce SIP, I studied up on oxygen permeation into soil, and the need for roots to have access to oxygen—what is called "root respiration". This is necessary for the biochemical processes that create the cellular energy that drives both water and nutrient uptake in the roots. In other words, roots love oxygen. If they don't get enough, because the soil is impervious to air, or because of too much water in the soil, this shuts down growth and also invites disease due to the anaerobic environment.
So in my design I maximized the surface area of the air-to-soil interface, by putting a lot of small holes in the domes, both on the top and on the sides. I call these the "air/water vents". The holes have a dual-dual purpose—air inflow/outflow and water inflow/outflow. As the reservoir level goes down, more holes provide air to the root zone. When the reservoir is filled down the tube, the water level in the domes rises, pushing air into the medium.
Another very important dynamic is the composition of the soil medium, which must accommodate good air flow. This is why it's very good to use lots of coconut coir, and a good amount of perlite as well. Keep in mind that on the microscopic level, the soil medium has lots of air space between the solid particles. The root filaments inhabit these spaces where they have plenty of access to oxygen.
More photos and details about my design
HERE.
The heart of the Triforce SIP—three domes D1, D2, and D3. Note that there's a friction fit on the fill tube connection to D1, so that it can hover in place in the air pocket. When the bucket is filled with soil and in use, the fill tube can be adjusted slightly up or down no problem.
#2 food grade HDPE plastic yogurt container.
The shaded area is what I call the "R zone", where roots have access to the saturated medium in the reservoir, and also have access to the air vents. This R zone is much larger than in other SIP bucket designs, and provides a large wicking area as well.
So far, so good...
A CBD clone recently transferred to the flower house. This is the first plant I've flowered in a SIP. She's drinking very well and doing great. The reservoir holds about a gallon of fertigation water, which gets used up in 1-2 days.
HI-BISCUS comparison grow, Triforce SIP on the left. I'm at the point where the reservoir needs to be filled every 1-2 days—fertigated down the tube. The big lesson in this first SIP grow was that fertigation should have been started at 2 weeks into the grow.
