I have a Fluval Roma 125L aquarium and it comes with a U3 filter .. i have silica sand in my tank and every day it needs vacuming .. i only feed the fish once a day but thus akes no difference, Does any 1 else have this problem with the U3 filter not picking up debris/waste ect? just seems to me like it aint doing its job at all? Any help wud be great Thanks.