To maintain healthy environment in the tank, substrate should be cleaned regularly, too. Many aquarists neglect to change the substrate, not knowing that bits of fish food and waste often collect in the substrate. The waste causes bacteria and algae to grow, causing the water to become cloudy. 

Aquariums with gravel bed should be cleaned at every water change to remove organic matter trapped in the substrate. Doing it is not as complicated as many think, but you need to have the right tool for the job. The best way do clean substrate is to use a gravel washer. A gravel washer is 2” diameter tube that easily fits into the mouth of a siphon hose. An alternative tool is the siphon gravel. Some cleaning systems have hose long enough to allow you to hook it directly to a sink; they use water pressure to drain water from your tank to the sink drain. If you have a short siphoning system, use a bucket. Never gravel through a filter or water pump and take extra care not to disturb the root systems in your aquarium. 

Remove half of the decorations in your tank before vacuuming the substrate. Don’t vacuum in haphazard manner. Do it in rows, starting from front to back. Gravel clean each row thoroughly before proceeding to the next. Gravel as much as possible, but once you have reached the required amount for water change, stop vacuuming. Put the decorations back into the tank, introduce fresh water, and wait for the next water change to continue what you have started.