I have been a fish hobbyist before. I had kept freshwater fishes ( assorted, pure goldfish tanks (even bred goldfish), pure discus tanks, saltwater and even coral reef tanks).I got diff sizez of aquariums and my largest is a 100 gallons one measuring 6 feet in length. The key is not to overcrowd your tank and plant plenty of water plants. as long as hindi overcrowded ang tank, ok lang kahit mga-brownout or even walang filter or powerhead (except for coral reef tank) coz the oxygen content of the water will be enough for the number of fishes plus the plants will also give off oxygen.ang puurpose lang naman ng aeration is to keep the surface of the water moving so there will be exchange of air. there are some fish hobbyist in other countries who advocate natural fish tank without any artificial filter.nun nasunugan nga kami and we had to vacate the house for 1 month, 1 month din walang kuryente but buhay pa din ang mga fishes ko