How to Stock an Aquarium With Different Levels of Fish

Size and Type of Fish Matter

stocking aquarium fish evenly illustration

The Spruce / Mary Mclain

One of the factors often overlooked when choosing fish for a community aquarium is the swimming level the fish prefer. Choosing fish that prefer swimming at different levels will result in a far more attractive aquarium, while at the same time assuring that your fish will not have to compete for space. It will also reduce the stress that occurs when fish have to battle for territories.

Popular fish that swim at any level include:

Top-Level Fish

Top dwelling fish add movement and color at the top level of the aquarium, which often has very little decoration. Many fish that prefer the top level are surface feeders in nature and have upturned mouths designed for top feeding. They hang at the surface waiting for the next meal to come along.

Keep in mind that some of these top-level species are strong jumpers. Hatchetfish are known for being able to leap several feet out of the water. Even fish that don't normally jump may do so when startled by loud noises or sudden movements. Take care to keep the tank well-covered, and close the lid promptly after feeding or performing maintenance.

Popular top-dwelling fish include:

  • Marbled and Silver Hatchetfish
  • Halfbeak

Popular top to mid-dwelling fish include:

Middle-Level Fish

The middle level is the focal point of the aquarium and should be populated with plenty of active fish. Schooling fish, including most of the Tetra species, as well as some of the Barbs, are excellent for the middle level of a community tank. Mid-dwelling fish are often selected as dither fish for cichlid tanks, particularly schools of active fish.

Larger fish such as Gouramis, Rainbowfish, or Angelfish also make interesting mid-level fish. However, it is important to remember that slower-moving fish with long-flowing fins may be picked on by smaller, faster-moving fish. Tiger Barbs are particularly well known for nipping fins. Avoid combining them with Angelfish or Bettas. Also, remember that many Gouramis aren't tolerant of their kind, so do your homework before adding them to the mix.

Popular mid-dwelling fish include:

Bottom-Dwelling Fish

Bottom-dwelling fish lend interest to the lower levels of the tank and often help turn over the substrate. You will note that most of them have mouths that point downward, making it easy for them to scour the tank bottom for morsels of food. However, do not fall into the commonly held myth that bottom dwellers do not have to be fed. All too often bottom-dwelling fish are under-fed. They cannot subsist only on leftovers from the other fish but must be fed with foods that will reach them on the bottom.

Remember that the top- and mid-dwelling fish will get to the food faster. Including sinking foods when feeding will ensure that those living in the lower portion of the tank receive enough food. Some bottom-dwellers are nocturnal and should be fed after turning the lights off for the night.

Popular mid- and bottom-dwelling fish include:

Popular bottom-dwelling fish include:

Choosing Fish

Always research the fish you are interested in for your community aquarium. Although swimming levels are a factor; water parameters such as pH, temperature, and water hardness are quite important when combining fish in a community aquarium. Also be aware of the adult size the fish will grow to, as most fish are sold as juveniles still.

For a quick reference, look at a level chart for a list of about 100 community fish separated by the level they prefer. Don't forget that your fish must also be compatible with preferred water conditions, size, and temperament.