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Don't turn off your filter unless absolutely necessary for example when cleaning it (which is very beneficial to the efficiency of the filter as long as it is done in dechlorinated water). Within 2 hours of water flow stopping (e.g filter being turned off) all your bacteria will be dead and you will be starting a fresh cycle when flow resumes. The water flow brings the oxygen needed by the bacteria and also its food source (Ammonia).
75 Litre (20 Gallon) - 5 Harlequins, 6 Cories, 2 Golden Barbs, 1 Glowlight, 2 Red Wag Swords (Male and Female), 4 Otos
113 Litre (30 Gallon) - Empty (Waiting to build a stand before i use it)
60 Litre Hex - Empty