You can use those alternatives like lava rocks and aquaclay media (they look like hydroton LECA balls and probably work the same)... they will work as base substrate layer to create more places for beneficial bacteria to live in and encourage healthy root growth.
Just have to work out if using alternative base media with separate additives is more worth it than compared to using powersand special.
Don't use coral chips though, as they raise pH... those will counteract the pH reducing characteristics of the aquasoil and exhaust the soil's buffering ability more quickly.
The only disadvantage of using such base layers is they tend to pop up above the soil substrate when you do adjustments in plant layouts and regular plant maintenance (ie. topping and re-planting stem plants), so you'll need to spend abit more extra time to push the individual base layer pieces back underneath. Looking forward, it also makes recycling the aquasoil abit more difficult too, as they will be all mixed together during tank de-comm.
Other than those considerations, such base layers do help in improving long term plant growth, especially for rooted plants and heavy root feeders.
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