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What bulk substrate to use under aqua soil and gravel


New Member
2 Nov 2022
Have bought some Tropica Aquarium soil and mesh bags. Going to be placing it under my existing gravel in stages. I also think I want to raise the back up higher than currently possible with the gravel and aqua soil I have.
Driving to multiple locations for a good match to my existing gravel has been fruitless and has set me back weeks, so I now plan to use a bulk substrate in bags underneath the aqua soil where I need height and then use my existing gravel to cap.

If I am going down this route, the bulk substrate might as well give an additional benefit over plain gravel, so either optimal for bacteria (alfagrog?? crushed lava rock?) or nutrient storage/release to roots (akadama?? clay balls?).
I've read plenty of threads on here plus the Substrate article but am not sure what route to go down and opinions on stated claims v actual benefits not that clear. What are people's thoughts?
Seems overly complicated. Just use an all in one substrate like Amazonia AS or Tropica AS. You can bank it as deep as you want no fuss. Failing that depending on your budget you could go all out ADA system or just use pumice to bulk it out. But there’s no real need.
Lava rock in net bags has always worked well for me in the past when I've wanted to create background height

No benefit other than its cheap and stable to build on, saves using silly amounts of expensive soils and it can be washed and reused