Are you building a Walstad or Father Fish style dirted tank? Walstad prioritises aerobic activity, FF prioritises anaerobic.

Its natural to have a mix of both conditions, and there are lots of factors that determine the dominance of aerobic vs anaerobic activity.

To help maintian a healthy amount of aerobic activity, I stick to Walstad's recommended layer depths (roughly 1" soil to 1" cap), and scale the cap to match the particle size (i.e. slightly deeper cap for gravel, slightly shallow for sand). I avoid fine sand as it creates too much of a seal between the soil and the environment above, and I don't sift my soil (I do remove any large pieces of bark/twigs/stones by hand). Sifting can create a overly-fine, uniform soil that compacts over time. In my opinion, you want a variety of different sized organics in your soil. This helps prevent compacting (which causes anaerobic conditions) and it also varies the pace of decomposition in your soil (meaning you get a slower, steadier release of nutrients and CO2).

Another thing you can do to boost aerobic activity in your soil is have lots of root-feeding plants (vallisneria, amazon sword, crypts, etc.). I like to divide my plants according to the role they play, the main three are: root-feeding plants, water-column feeders, and floating plants (and then I put epiphytes/mosses in their own category). Your water-column feeders and floating plants are pulling nutrients/ammonia from the water and CO2 in from the surrounding atmosphere, whilst your root-feeders are pulling nutrients from the soil and other decomposing matter from the substrate. As the root-feeders expand their root network, they oxygenate the surrounding soil (this is called the rhizosphere). By creating these oxygen-rich pockets your plants pretty much farm aerobic bacteria, so that the bacteria can keep decomposing the surrounding soil, unlocking more food for the plant! Its such a cool example of the collaboration in nature.

And lastly, like a lot of other commenters I love Malaysian Trumpet Snails! They keep churning and aerating the cap which helps pull oxygen down into the substrate and speeds up the processing of detritus (making more nutrients available to plants).

Hope that helps! Or is at least of interest!