Join Date: May 2020
Location: Southeastern US
Sandy loam has a very specific definition, generally it's at least half sand, a good bit of silt and very little clay. There are a range of proportions, and if you fall outside you end up in other soil types - look up the soil texture pyrimid to see where the boundaries between types are. There is a very small range where it's just sand and clay, but the clay must be between 15-20% or it's a something else like a sandy clay loam, or loamy sand, or sandy clay. They sound comically similar, but they all have different properties.
But I'm not sure if these soil types will make a great cap in an aquarium, even if it's authentic.