Setting up two Canister Filters can help increase flow in the aquarium. It can contribute to water clarity, reduction of debris and therefore lower nitrates, rotting organics and ammonia levels. Canister filters should generally turn over at least 5x the aquarium volume per hour on the low end and 10x per hour on the higher end. Any lower than this and they fail to function correctly. The aim is to stir up the water enough to dislodge rotting debris and force them into the intake, but not too much that you disrupt the natural feel of the aquarium and disturb the fish. Two intakes can be a perfect middle ground to solving this issue. Outlets can be used to disrupt both the surface and substrate in this case, without increasing the flow too much in a single direction.
Not only this but 2x filters offers a safety net. If one filter fails, the tank’s dissolved oxygen will decrease. The heater will have no flow to move warmed water. It is a dangerous situation and can be avoided with the use of two filters.
Two identical canister filters should be purchased that equate to a flow rate of at least 6-7x the tanks volume per hour. Eheim are an excellent brand, reliable and affordable within reason of a high quality product. Fluval, AquaOne and other cheaper brands will also work well. Be sure to read reviews before purchasing a filter – it’s the crux of your aquarium!
Set up the filters as normal. Add the filter wool, fill up the media baskets and securely connect the inflows and outflows to the canister filter. Each canister filter should be placed on either side of the aquarium. This way you have the added benefit of consistent flow from each side. The intakes can be placed on the same side as the outflow. Each side of the aquarium should have one intake and one outflow.
With one filter there is difficulty in where to point the flow. Without surface agitation, disolved oxygen levels will decrease and surface scum will also increase. This surface growth can also reduce light penetration to the aquarium.
But with two canister filters we can fix this problem. One of the outlets should be pointed toward the surface and the other toward the substrate. We end up with consistent and strong flow on all levels of the aquarium. This will help reduce nitrates and ammonia levels.
If you’ve been thinking about using two canister filters but weren’t sure. It’s time to switch. Two canister filters have a world of advantages with only a slightly higher starting cost.