Thanks for the inputOohhh, pretty stuff @sjb504 very pretty stuff. Thanks for sharing that one.
Yeah, I still drop the odd air pump in there still but there's no need per say.
They can help if you feel things have become overwet. And I use them in a lot of active-microbe grows which, these days, is most of them.
I only use on a burst timer schedule, so they are off for the vast majority of the time. Often I'm just keen to prevent any settling in the reservoir. As it can be a large reservoir, often it can settle out over time if not stirred up a bit and an anaerobic environment can develop over time if enough settling material is in the water to eventually isolate itself from the rest - and bad things can happen. So to have the benefit of of all the stuff I have in the water but not the threat, I run an airstone in my SIPs for a few seconds every few minutes - type of idea.
If you are running a fertigated tank, some fertilizers are more pH stable than others, and running an airtstone nonstop can impact your mix's pH, but frankly, making sure its just on a burst rate will prevent all but the most unstable fertilizers from reacting.
If you're just adding water to your SIPs its of no concern either way, in my experience. An airstone in operation will heat the water (which reduces oxygen content) while adding oxygen content - so it's a bit of a wash really.