salt deposition in sponge of sponge filter will decrease its efficacy. salt deposition in the sponge filter occurs if water has more Total Dissolved solids(TDS)
if all pores of the sponge get clogged, there will not be any filtration of water in the tank.
The water will not be crystal clear and look turbid.
so, check your sponge of sponge filter today itself.
watch the illustration video to understand the deposition of salt and a solution for the problem.