This may not be an option but I have a 300g water holding drum for my pool pond to do 50% water changes. I use a 1/2hp sump pump and 1.5" pvc pipe. I fill 300g in 3 minutes.
I use a swim pool hose that's about 40mm diameter with a tap at the end to keep the hose primed when shifting. To start the siphon initially I fill the hose with a water tap. There are some convenient fittings like extendable poles, stiff brush heads, rubber suction mouths etc that can be used with.