Yeah, I doubt garden hose pressure will do much in removing hard growth. However, a pressure washer ( around $80-100) from Harbor Freight with a wide angle nozzle may do he trick. It probably won’t remove slime, but should remove harder growth and moss etc.
They usually come with an table nozzle and a 50’ hose. You’ll need a 110v power supply and don’t let it fall in the water
while anyone is.