Hi,i kinda wanna change my filter from internal filter to an external canister that is fluval.my tank is 180 litres and i was confuse should i take fluvel 204 which can filter 600 litres of water per hour and its maximum capacity is 200 litres or fluval 304 which can filter 100 liters of water per hour and can filter 300 litres of water???Its for a 90x45x45cm tank