Years back I was able to purchase some pond "soil" at Lowe's & Home Depot.
It was made by Scott's, I think. It was ceramic particles actually and not
soil. It was nice because it did not float or cloud the water and should the
Koi uproot the plant it was easy enough to scoop into the basket and replant
the whatever.

I guess I could use very small pebbles like you can get for landscaping but
I wanted to check in with you guys first.

TIA

JB