I believe you're taking about the 13 litres IQ5? When someone recommends a 6 month period, it's putting into consideration that the water has stabilised... And when anemone dies, it produces a toxin which can potentially wipe out all fishes and corals and invertebrates... Considering a 13 litres tank, changing 200% water wouldn't be a problem... But for a full setup of 50 kg live rocks and 700 litres of water, it would prove costly and time consuming... Not to mention the livestock...