For most aquariums, performing a 25-30% water change every 1-2 weeks is recommended. However, this can vary based on tank size, fish load, filtration, and water test results. More heavily stocked tanks may require more frequent changes, while lightly stocked tanks with robust filtration might need less frequent maintenance.

Cycling an aquarium establishes beneficial bacteria that convert toxic ammonia (from fish waste) into less harmful nitrates. Without this nitrogen cycle in place, ammonia will quickly build to levels that can harm or kill your fish. A properly cycled tank is essential for fish health and typically takes 4-6 weeks to establish.

Some fish species can coexist peacefully in community tanks, while others cannot. Compatibility depends on several factors including size, temperament, swimming level, and water parameter requirements. Research each species carefully before combining them. As a general rule, avoid mixing aggressive species with peaceful ones, and ensure all fish in a community tank have similar water parameter needs.

Signs of illness in fish include unusual swimming patterns, loss of appetite, visible spots or growths, frayed or clamped fins, rapid breathing, hiding more than usual, and color changes. If you notice any of these symptoms, first test your water parameters as many health issues stem from poor water quality. If water parameters are normal, research specific symptoms and consider consulting with an aquatic veterinarian or experienced fish keeper.