Water change mistakes that kill fish and crash bio-filters.
Single water changes >50% can shock livestock from sudden parameter shift. Split into 2-3 smaller changes over a week instead.
Chlorine + chloramine kill bacteria. Always treat replacement water with Prime/dechlorinator OR use pre-aged RODI.
Adding cold water shocks fish + corals. Match replacement water temperature within 1-2°F of tank temp before adding.
Tanks accumulate nitrate + phosphate over time. Even with low bio-load, do at least 10% monthly to refresh trace elements + buffer.
Beneficial bacteria live in substrate. Vacuum 1/3 of the tank per water change, not the whole substrate. Skip planted-tank substrate vacuuming entirely.
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