well the problem is this, the hanging filters will not be submerged in water that will be aeriated by the air stone. Anyone will tell you, you shouldn't turn the filters off at night but if you find it nessicary then, it would be ok. the bacteria in the filter sponges will most likely die unless the are unaerobic bacteria, but there will still be plenty of bacteria in the tank and it would stay at a high enough level in that size tank. with turning off the filters, you may get a smell from the stagnent water and the debris in the sponges on the hang-on. It will depend. you will also have to do more maintainance on the filters, but if you need to the nit would be ok over night. Also when feeding your fish make sure it is about 2 hours before turning the filters off, this will mean that the fish will have had enough time to digest the food and poo, and then the filters will be able to suck it up, this means you will not get an amonia spike. also i doubt that you would get an amonia spike, the bio load just isn't that big, and it would take longer than 12 hours for the tank to start to produce ammonia or nitrite or even nitrate bacteria.