Why does this happen and how do I prevent it?
The water level of your aquarium will fluctuate. Most cases of dropping water levels are simply evaporation, usually caused by higher temperatures in warmer climates. If you have an open topped aquarium consider using an evaporation tray in summer to reduce water loss. However, if you are noticing large drops in water depth it is important to check for leaks in the aquarium keeping an eye open for water damage on the cabinet, walls or floor around your aquarium. Regular top ups of fresh tap water treated with Bioactive Tapsafe plus are recommended but this should not replace regular water changes.
What treatment should I use?