I changed my pump on my jewel aquarium 180 from a 600 to a 1000 and added a 205 litre canaster filter to my tank which is also about 15 inches over stocked. The canaster filter takes up no room in the tank and the which is always good when the tank is over stocked (apart from the small pipe and outflow pipe). This was a slightly expensive solution but water conditions are always perfect ie amonia
nitrate nitrite 0ppm. It is probably over kill on the filtration but better that than sick fish !!!!!!!
ps. have a small 105 air pump with a 2 inch stone in the tank. does the job for me.