Health & WellnessWhy are my fish dying with pink and green algae in their tank?
Check the water chemistry using a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence (0 ppm) of ammonia and nitrites with nitrates at 20ppm or less. Perform partial water changes to stabilize chemistry and/or to improve water quality. Rinse the filter media in tank water, not tap water, and replace it. Use only conditioned water that is temperature matched to prevent stress or shock. To limit algae growth, maintain pristine water quality via filtration and regular water changes. If possible, turn up filter flow to keep water moving. If this stresses the fish though, do not do it.
Do not overfeed and remove any uneaten food promptly. Limit lighting to 8 hours daily and closely monitor water temperature as well. All these can promote algae overgrowth.
Updated on September 24th, 2025
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