Can I use another type of sand instead of the really expensive silica sand?
I would definitely NOT recommend using sand in a Koi pond. Koi fish play around in the substrate a lot. Sand will get into their gills and act like little bits of glass. Not good! When that sand starts getting dirty and it will get very dirty, you will regret using sand. Opt for a bare bottom in the pond. They’re much easier to clean.
