What to Keep in Mind When Changing Water for Your Arowana

1 Pre-Condition the Water

Treat the water to remove residual chlorine from tap water before using it for your arowana. Chlorine is typically removed by leaving the water in sunlight or aerating it vigorously. Pre-conditioning usually takes about three days and should not be drawn out much longer than that. Fresh tap water carries a high chlorine load and must never be used directly for keeping arowana, as it will harm the fish.

2 Avoid Large, One-Time Water Changes

During keeping, the keeper must maintain stable tank water and never replace a large volume all at once. Doing so causes a sharp swing in temperature, pH, and other parameters, which can stress the arowana and lead to refusal to eat. Instead, change small amounts repeatedly so the fish gradually adapts. Start by replacing about one-eighth to one-sixth of the water, then top up with smaller amounts at intervals. Aim for a steady rhythm, such as every two or three days, to keep water conditions relatively stable while giving the arowana time to adjust. Also keep the temperature steady by holding the difference between new and old water within 1°C.

3 Keep the Movement Gentle and Slow

When changing water, never make abrupt movements or let a strong current wash directly over the arowana’s body, as this easily damages its skin and raises the risk of infection. Avoid stirring the water forcefully, which can create excessive pressure and harm the fish’s internal tissues. Place the filling tube at the bottom of the tank and point its opening toward the glass wall, minimizing the fish’s exposure to water flow. This point is very important and should not be underestimated.

4 Do Not Feed Around Water Changes

Do not feed the arowana for about three hours before and after a water change; if the day happens to be rainy, you may skip feeding that day. After water conditions shift, arowana typically lose their appetite and only resume eating once they adjust to the new environment. Since a water change inevitably alters water quality, even if only slightly, hold off on feeding for a while and wait until the water stabilizes and the fish has fully adapted before offering food again.

5 Observe the Arowana After Each Change

After every water change, watch the arowana’s condition closely so you can spot any discomfort caused by the change and step in with the right help promptly.

Many common arowana illnesses are tied to water quality. Good, stable water promotes healthy growth and is a basic requirement for keeping the fish well. Keepers should always take water quality seriously, follow the guidelines above, and maintain clean, stable water to reduce the onset of disease.

The points above are the key precautions for changing an arowana’s water. Make sure you master the correct method so the fish stays healthy after each change.