What to do if your water is too acid or too alkaline

Stability often beats “perfect”

Many fish tolerate a range of pH as long as it's stable. Sudden swings are more dangerous than a reading that's slightly off. Before you try to change pH, ask: are your fish actually stressed or sick, or did a test just show a number you don't like? If everyone is healthy and the number is consistent, sometimes the best move is to leave it and track it in App-aquatic.

Water too acid (pH too low)

Common causes: soft water with little buffering (low KH), driftwood, leaf litter, or lots of organic waste. To raise pH gently: add crushed coral or limestone in a bag in the filter or as decor (they dissolve slowly and add carbonate, which raises KH and pH). Water changes with harder tap can help if your tap has higher KH. Avoid dumping chemicals in to spike pH — it can swing back and stress fish. Fix the cause (e.g. remove or boil driftwood if it's pulling pH down more than you want).

Water too alkaline (pH too high)

Common in hard tap water or tanks with crushed coral, limestone, or coral sand. To lower pH gently: use peat (in a filter bag), driftwood, or Indian almond leaves — they release tannins and can lower pH over time. Mixing with RO or distilled water (and remineralising as needed) dilutes hardness and can bring pH down. Again, avoid dramatic chemical fixes; slow, stable changes are safer. Some fish (e.g. many tetras, rasboras) prefer slightly acidic water; others (e.g. livebearers) do fine in harder, more alkaline water — so choose fish that suit your water when you can.

Quick takeaways

• Stable pH is often better than chasing a “perfect” number.
• Too acid: add buffering (crushed coral, limestone) or do water changes with harder tap.
• Too alkaline: peat, driftwood, or softening with RO/distilled; choose fish that suit your water when possible.