Originally Posted by 10gallonplanted
Here is my hardscape so far.
You have gathered some awesome materials to work with and finally the weather is giving you a chance to get busy with it
Want to throw out a couple questions / concerns and hope that's O.K. with ya?
How thick a soil layer did you use?
How did you mix or set things, amounts used if mixed (ratio of the mix)?
It looks like a layer of the clay litter box material is showing below the cap and I'm wondering how you combined the materials.
How thick is the cap? Is it a combination mix of the Eco-Complete and black Diamond? Is the total substrate base thicker than 3"? (hard for me to gauge total depth in pics)
From things I've done here and reading the posts of others I would have a concern about decomposition gasses being trapped under large areas blocked by the rocks used in the scape. Soil / capping layer thickness greater than whats the average used can be a concern too. All soil mixes with organic content bubble for months, actually nearly a year in my experience dirting tanks but I consider that a good thing. My concern is if large areas under rocks aren't allowed to release then the bacteria can suffocate in the gas byproducts of organic decay (bad thing). When I've used large rocks in the scape setting up new tanks the soil layer is placed around (not under) large rocks. Under the rocks I used capping materials only. It's not just about whether anaerobic conditions are allowed it exist within the substrate (anaerobic bacteria always
develop). The bacteria that consume organic materials releasing the mineral goodies for our plants generate a bunch of CO2 in the process. Trapped in the substrate that's not good thing either. Allowing the gas exchange is important with this type of setup. Several times I've had pretty large areas of the substrate start mounding into little hills. Poking into the base with planting tweezers released a bunch of trapped gasses (no hazard) and once it was released that was the end of it as far as it being a concern. Left in place or trapped until it builds up finding a way to burp can cause some problems.
Some soil and capping layer thickness averages based on the materials used.
MGOCPM 1.5 to 2" maximum depth.
Sand or blasting grit 1 to 1.5"
Fractured clays and rocks like Flourite or Eco-Comp not more than 2"