Mind you I only have river-rock as a bed in my aquarium and do not have layers of different sub-straight. I also have Goldfish in my tank.
specifically because you have large gravel, and large poop factories for fish,
you need to vacuum much more often than the average planted tank keeper.
large quartz gravel does a poor job hosting the bacteria and microorganisms
helpful at breaking down poop and left over food, thus the junk accumulates.
if you had 3" depth of 1-4mm grain size substrate, preferably volcanic or clay,
you would not need to vacuum at all
as long as you also under feed your fish.
so a tank with proper substrate should not be disturbed or the large amount
of mulm (fish & plant debris, bacteria & microorganisms) deep in the substrate
will become water bourne and disturb your fishes health, as well as temporarily
reduce the effectiveness of your substrate as a biological filtration system.
as for how to clean a spong filter - I never squeeze mine.
I place them in a half gallon jar half full of water, then
I close the lid over the jar, and shake it around a while.
I pour out the waste water, then put back the sponges.