Kevin
Check out the pore size on the sponges. Hydro sponges come in at least four different pore sizes. The fine-pore size works very well and for a long time but cleaning it out is very difficult. The very large size pore as found in the pond or prefilter sponges allows good flow and lots of places for good bacteria to grow and is hard to get packed with debris and is easy to clean but can allow the tank to remain cloudy. The other two pore sizes are between these two. I prefer the larger size pores but not the prefilter size. BTW if the tank was clean and then becomes cloudy after a month or more with a sponge filter, that is often the result of the sponge filter being clogged with debris and therefore in need of cleaning. Once cleaned the tank will still take a couple day to become clear again, maybe less time if you also do a large water change.
Frank