Which of the following conditions can result in the need for routine water testing in fish tanks?

Routine water testing in fish tanks is essential for maintaining a healthy aquatic environment, and ammonia management is a key aspect of this. Ammonia is a highly toxic compound that can accumulate due to fish waste, uneaten food, and decaying organic matter. Elevated ammonia levels can lead to serious health issues for fish, including gill damage, stress, and even death. Regular testing helps ensure that ammonia levels are kept within a safe range, facilitating prompt corrective actions if levels rise.

In contrast, while high pH levels, excessive algae growth, and frequent water changes can influence water quality, they do not specifically necessitate routine testing in the same way that ammonia management does. High pH levels can affect fish health, but they are more of a secondary consideration once ammonia is controlled. Similarly, frequent water changes can help dilute harmful substances but do not replace the need for routine testing to monitor water quality. Excessive algae growth may indicate underlying issues, but again, managing ammonia levels is more critical for the immediate health of the fish. Thus, ammonia management is the primary reason for the necessity of routine water testing in aquaria.