Angelfish, discus and South American cichlids live in slow moving blackwater streams. Bettas and gourmais live in Southeast Asia slow moving streams. They are more comfortable in tanks that feature gentle water movement rather rapid moving water.
Hang On The Back Filters
There are several styles of aquarium filters, but the hang on the back is the most popular. If the filter is sized for the tank, the flow is slow enough for these fish. Some hob filters have a flow control adjustment. Some are preset and allow 3 or 4 flow settings. Others are infinitely adjustable. This is a feature to keep in mind when purchasing a hob filter.
The best hob filter is the Rena Smart Filter. It uses pressure to force water through the filter medium to deliver crystal clear water. Some users recommend a pre filter sponge on the intake to allow the main filter to last longer. That can be recommended if the tank is populated with fish that eliminate a lot of waste. The Smart Filter has a flow adjustment.
Restricting HOB Flow
If a hob filter doesn’t have a method to reduce flow, some hobbyists use other methods to reduce flow. Cut the toe off a pair of clean pantyhose and put it over the intake tube. Secure it with a rubber band. This reduces the amount of water entering and exiting the system. This also prevents small fish from getting sucked into the filter. Another method is to use foam or mesh at the outlet into the tank. This diffuses the water as it goes into the tank. When modifying, watch that the reservoir doesn’t back up so that the filter overflows.
Power heads are used to increase flow and aeration in the tank. These allow adjusting the water to a higher or lower flow. Air stones in an undergravel filter provide a slow gentle flow good for black water tanks. Power heads can be used on undergravel filters instead of air stones if more flow is desired.
Canister filters sit in a cabinet or on the floor behind the tank. These have adjustable flow rates. Some have adjustable rates to allow higher rates at different times of the day. Canister filters are the best choice for tanks over 100 gallons. Magnum, Eheim and Fluval are among the most popular, but Rena Filstar and Sunsun aren’t as well known, but are some of the best canister filters.
Internal filters are submerged in the tank. These filters have adjustments to control water flow. These filters are best in smaller aquariums, or supplement another type of aquarium filter.