i want to buy an air pump for my 90 gallon cichlid tank,i'm running a top filter with a LPH of 300lt/hour.i have a albino oscar with 4 silver dollar and a red parrot in it.want to keep a back up with a air pump which will be connected to sponge filter or bubble stone. please suggest what kind of air pump should i buy? it must be long lasting,heavy duty air pump and must be at affordable price.thanks