Weekly, biweekly and monthly maintenance is an important part of keeping a healthy aquarium.
Water Changes
Water changes are essential to a successful aquarium.
A water change should be performed approximately every two weeks. Usually, 10-15% is enough.
It is essential to check the new water you are introducing to the aquarium. Tap water can contain chlorine or chloramine, which must be eliminated before adding the water to the tank.
Local tap water can also contain phosphates, iron and other heavy metals. Call your local water company to find out about your tap water chemistry.
Testing
It is essential to check water chemistry on a regular basis. The vital parameters to test in your aquarium are pH, nitrates, nitrites, carbonate hardness and, for marine tanks, salinity.
pH should be at 6.5-7.5 for most species.
Nitrites should be zero at all times (except during cycling). If nitrites are detected make sure you check your ammonia also.
Nitrate should be kept below 10 ppm in freshwater and 5 ppm in marine and reef (preferably 0 ppm).
Recommended Maintenance Routine
Daily
Be aware of how your fish are acting. Changes in behavior can indicate a potential problem.
Check your equipment to ensure it is running properly.
Weekly
Keep a current inventory of the livestock in your aquarium.
Dead animals can decompose very quickly, which can easily cause an ammonia and/or nitrite spike, which then leads to high nitrate levels.
Biweekly
Test your water for:
pH
Ammonia
Nitrite
Nitrate
Salinity (in salt and reef tanks)
Vacuum the gravel and change 10-20% of the water.
Clean the aquarium glass.
Rinse filter cartridges with the water you pulled from the tank.
Replace carbon and filter floss (if present).
Inspect all equipment and parts for proper operation.