I just want to add how high and how thick the hose is will also effect the flow.
These bilge pumps are not made to push water up, only out, so a foot of height difference will make a visible difference wit the flow. My gold cube is a three stack tray that sits on top of a five gallon bucket and works fine. Also need to stick to the hose size the pump is made for.
To prevent organics and silt from clogging the pump, I use a five gallon bucket to catch the tailings which drains in a 20 gallon cement mixing tub my gold cube its in to catch muck, which drains to a 10 gallon tub, where my pump sits wrapped in a mesh. I've used different things for mesh to a narrow mesh I got at hobby lobby to panty hose.
Also, are you running regular dirt or a black sand concentrate?