Detritus is considered to be any disintegrated material, waste, or debris that is present in aquariums. Most often, the term refers to organic matter produced by the decomposition of organisms. Examples of aquarium detritus can include dead or decomposing plants or aquatic life, molt coverings discarded by inverts such as shrimp, animal waste, and uneaten food.

If left untreated an accumulation of detritus can cause nitrate and phosphates to rise, that could cause algae outbreaks in aquariums where there was none. If left unchecked, the nitrogen waste can become so high it becomes lethal to your aquatic life.

Dead or decomposing detritus sometimes displays as brown matter or more simply, as “gunk” in your aquarium.

Natural occurrences such as aquatic life death, decaying plant matter, dirty filters, overfeeding, overstocking, and not performing routine water changes can cause or extend the presence of detritus in an aquarium.

Prevention and physical removal - There are steps an aquarist can take to lessen the presence of detritus in their aquarium. Since leftover food is a large contributor to detritus, restrain from overfeeding your aquatic life. Also, maintaining good filtration and regular water changes can help. Physical removal of dead plant matter can also help. Vacuuming or siphoning your substrate can also help.

Live predators - Another method of removal is with the use of aquatic life that feeds on detritus.

There are many fish and invertebrates that consume detritus. A few are mentioned below.

Freshwater

Corydoras
Cory Cats are some of the most peaceful and entertaining scavengers for a freshwater aquarium and will thrive in a wide range of water conditions. These catfish are very energetic scavengers who remain relatively small. Because of this, they are perfect for keeping the substrate clean in a smaller freshwater community aquarium.

Plecos
Members of the Loricariidae family of suckermouth catfish, Plecostomus, or Plecos, have specially adapted mouthparts, enabling them to attach to substrate. Most Plecostomus are peaceful fish and prefer to rest or slowly graze over the aquarium bottom and do an excellent job of cleaning unwanted algae and detritus from the bottom and sides of the tank.

Freshwater Invertebrates
Because inverts spend all or a majority of their time on the aquarium substrate, they are close to the detritus that settles there, giving them an advantage in removing unwanted matter that settles. Snails and shrimp are particularly effective consumers of detritus.

Saltwater

Sand-sifting Gobies
Gobies are relatively small fish (larger species growing to 6”). Goby fish species adjust well to aquarium life. A well-sealed lid is a requirement for keeping Gobies, as they will jump out of an open aquarium. Plenty of rockwork and the proper substrate of coral sand should be provided to enable burrowing or sand sifting.

Marine Inverts
Diverse, interesting, colorful, and unusual, marine invertebrates make great additions to your home saltwater aquarium and can help control the accumulation of detritus in your marine aquarium. Like their freshwater counterparts, snails and shrimp are particularly effective consumers of detritus.

Aquascaping plays an important role in minimizing areas known as “dead spots” where water flow is minimal, and detritus can accumulate. Hobbyists can strategically aquascape around filtration equipment/powerheads to prevent this.

Establishing good habits with regard to water quality can prevent detritus build up. Staying diligent and removing matter that can become detritus is a strong second step, and getting some assistance in the form of aquatic stock that can help you will set you up for success in controlling detritus accumulation in your freshwater or marine aquarium.