I'm not sip-savvy Buds but I can tell you that lack of oxygen can and will lead to pretty much every nutritional deficiency there is if you are growing in living soil. Im not sure about synthetics but likely there too.
This is because when a nutrient is in the soil it has to be attached to an oxygen molecule for the system to recognize it as aerobic. Unattached it is anaerobic.
Microbes that prepare the food into plant friendly nutrition breathe air as well so without air you have no microbes to prepare the food. One part of the food prep is attaching that oxygen molecule.
Then there is your soil itself. Air is 78% nitrogen so if you are too wet, that air can't get in. No air, no nitrogen.
As for top watering, It is possible to do without detriment but only to the point where it refills your res to the desired level as the water will flow down. Too much and it will come out the overflow, but really that sounds counter-intuitive to sipping to me.
I use wicking, which really is a different version of sipping, but my res isn't attached, its a jar or bucket below the pot with wicks pulling the water up but still giving me that air gap. I also use cloth pots so over watering isn't possible.
As for perlite, think of it as a reef in the ocean, its a place that things (microbes) can hide and establish themselves into, but if you are using something else for aereation, such as rice hulls or whatever then you are still achieving the reef effect.
Perlite is inert so it goes round and round in my soil reammending without interfering so thats why its my preference.
Azi mentioned calcium. Its more than a nutrient. In living soil its the main ingredient as it sets the colloidal charge to fill the colloidal plates with the proper ratio of all nutrients (aka organic chelation, but as nature designed it, not General Hydroponics, FoxFarms, etc..) so if its low, then your soil kitchen isn't able to properly load those plates and what does get loaded can and will get locked out as the charge isn't correct so nutrients stick to each other.
Different foods get locked out depending on how low it is.
PH is what allows cec to release the nutes from the plates. Different nutes swap out with hydrogen at different ph's and fall off the plate (become available, no longer locked out).
Thats why Cal-Mag is such a good rescue tool. It corrects the chelation and it also neutralizes magnesium back to its needed electrical state.
When calcium gets low in the soil the cal to mag ratio gets out of whack.
Magnesium starts to get electrically sticky and ties up other nutrients. It likes nitrogen the most so low cal in living soil usually shows as a nitro def 1st.
Calcium also, by using its double positive charge, which makes it your strongest electrolyte, sets the floculation of your soil.
Think of your soil particles as dinner plates stacked in the cupboard and held together by magnetism. Changing the charge with calcium changes that magnetism.
When you hold 2 magnets together they stick. Turn one around and they repel but spin around and stick by their own means.
When Calcium corrects the electricity in the soil structure it changes the polarities in the particles and every 2nd plate in the stack stands on edge forming I-beam structures in the soil particles that become hallways for air,water,microbes fungi... you get the picture.
Inside those hallways are soil particles laying everywhere. Some are huge boulders, some are pebbles, some are sand. Capillary action of water prefers the sand 1st as small particles have more surface area and capillary action needs that.
Air prefers the large gaps between the boulders to rush thru uninhibited.
When you get your aereation and electrical charge correct you get the proper atmosphere for water and air, plus proper food delivery.
Having an external res fill an internal one is really just using siphoning so if your soil gets too wet I would make a 2nd overflow hole a bit lower to drop the gradient but....
Azi would be a better guy to help you there.
Here is a link to a video that explains a lot about soil basics, which need to be set correctly for a chance in living soil.
Post in thread 'The Gee Spot - You Finally Found It'
The Gee Spot - You Finally Found It
Hope that helps you out.
