Midwater fish: the heart of the aquarium

Midwater is often the busiest part of a community aquarium. Fish use it to travel, forage and interact, so leave a clear swimming route rather than filling every inch with decor. Plants and wood near the edges can provide shelter without closing off the whole tank.

Many small tetras and rasboras are schooling fish. Their social needs depend on the species, but a group that is too small can leave them nervous or withdrawn. Research the right group size alongside adult size and tank length.

Cardinal and glowlight tetras, harlequin rasboras and many other small species can create beautiful movement in a planted tank. Each has its own preferred water conditions and social behavior, so do not assume that all “small schooling fish” can be cared for in the same way.

Choose one species at a time, confirm it suits the aquarium and add fish gradually. Keep an eye on how they use the space, whether every fish is eating and whether tankmates are causing stress.

Angelfish and gouramis are striking examples of fish that use the middle and upper parts of the aquarium, but their needs are different from a small tetra’s. Adult size, territorial behavior, water conditions and the temperament of tankmates all matter. Some may eat very small fish or become more assertive as they mature.

Use a reputable care sheet for the exact species and keep a backup plan in mind if a community does not remain peaceful. If you are still weighing options, start with choosing compatible fish.

Use a complete food suitable for the species and size of fish. Offer modest portions, check that the fish you keep all get a chance to eat, and remove uneaten food. Overfeeding can pollute the water even when the fish appear eager for more.

Regularly test water quality and keep filtration working as intended. Continue to the bottom-dweller guide and surface-feeder guide to learn how the other water zones add to an aquarium.