The movement of water is an important factor when keeping any type of aquarium. Depending on how fast or slow the water moves is completely dependent on what marine life you are keeping or planning to keep in the tank. Many beginners find this topic to be a setback since they are unfamiliar with how water motion affects every type of species that we may find in our local aquatic shops. Some will require higher motion than others, while other species such as Seahorses need something such as a sponge filter with minimal flow. This article will be discussing how to plan your aquarium in regards to the speed that your water should be moving, and why it’s important to sustain life overall.

The Ocean

As all of you probably know, the ocean is constantly moving via currents and tides. Every pelagic zone in the ocean is under constant motion; whether it be from the sunlit zone’s convection currents or the abyssal zone’s turbidity current’s via sediment movement. Tides are also a necessary part of our oceans, in which high and low tides benefit certain species of marine life that need the oceanic levels to transition to maintain their longevity. High tides will make some fish more active, in turn increasing their food supply in particular areas. In relation, low tides will allow some species to acquire more sunlight that is needed for sustainability such as anemones and coral. Now that we understand this we can look at how the motion of water affects our aquariums.

Applying Motion to Tank Life

It is no surprise that those who have turned off their filters or pumps have seen fish die within a couple days’ time. Or those who keep freshwater and believe no filtration is necessary for Goldfish or Betta’s will see their fish die in a matter of months. But why is this? The answer to this is simple. Whenever water ceases to move, even in a perpetual cycle within a tank, the water is depleted of oxygen. Without oxygen in the water, nothing is able to survive. Fish and even invertebrates are constantly breathing in oxygen in water, much like we do air. Without any way to receive oxygen such as we see in a stagnant pool of water, then the fish will eventually consume all of the oxygen in the tank.

Filters and pumps act as a replica to the currents we see in the ocean. The breaking of tension on the water’s surface via water motion allows oxygen to be implemented back into the water itself. Therefore, suitability in any body of water is dependent on motion, regardless of what you may have been told in a pet store with the care of Goldfish or Betta’s. This is also why fish bowls are an impractical and cruel way to house any species of fish. The motion of water also allows harmful chemicals such as nitrites and ammonia to break down. Stagnant water only amplifies the toxicity of these naturally occurring chemicals, not to mention promotes bacterial and algae growth.

Setting Up Your Pumps/Filtration

The placement of your pumps is just as important as any other step in the hardware application of aquariums. You need to make sure that a good range of your tank is receiving some type of current, even if it’s low. The lack of current in any area can create what is known as water anoxia, which is essentially a dead zone in the water. These areas are typically spotted easily, as diatoms (the red-orange muck on sand beds) builds up in particular areas. If you see an outbreak of this, then chances are that the specific area in question is not getting enough oxygen via water current. This problem is an easy fix by just readjusting the pumps to ensure aeration in the entire tank.

Example of Diatoms


Which Fish Require High/Low Currents

Many fish benefit from either high or low currents as mentioned previously. Most can adjust to either, but some fish are more sensitive than others in regards to the movement of water. I will list a few examples below so you can familiarize yourself on how to prepare a tank for them.

Seahorses/Pipefish – Low current

Pufferfish – Low current

Anemones/Coral – Low to Mid current

Sharks – High current

Rays – High current

Jellyfish* – Low, circular current (Please leave a comment if you wish to pursue this species. These are incredibly hard to keep in captivity.)