Oscars are a messy fish, for sure
I think you could go smaller on the korellia's and vacuum the bottom weekly, or more often...
Thing about sand is, it will move with too strong of current, sometimes before the crud that sits on top of it...that, and it shows more debris that gravel that lets the stuff settle in the nooks and crannys...
I got a fine mesh, skimmer net, to "sweep" the bottom with, manually.
It helps keep the sand looking fresh...
I think you could go smaller on the korellia's and vacuum the bottom weekly, or more often...
Thing about sand is, it will move with too strong of current, sometimes before the crud that sits on top of it...that, and it shows more debris that gravel that lets the stuff settle in the nooks and crannys...
I got a fine mesh, skimmer net, to "sweep" the bottom with, manually.
It helps keep the sand looking fresh...