For best filtration, and the needs of your gold fish I would look into getting an overflow box setup in the bowl and at least a 5 gallon sump built. A 4 inch filter sock at one end, heater and pond matrix in the first middle area for Bio. Also throw an air disk with a good air pump in the next area with a moving k1 bed, and a pump for 10 times turn over at the end going back to the fish bowl. That would be the best filtration for your gold fish. And then once that is complete write back and I will help you setup an auto drip system to.get automatic water changes done.
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