Herbivorous fish play a vital role in freshwater ecosystems around the world. If you’ve ever wondered which fish species feed solely on plant matter or want to learn about keeping herbivorous fish in your home aquarium, you’ve come to the right place.
If you’re short on time, here’s a quick answer to your question: Common herbivorous fish found in freshwater environments include cichlids, plecostomus, goldfish, and some species of tetra.
Defining Herbivorous Fish
What Does Herbivorous Mean?
Herbivorous fish are those species that feed primarily on plant matter rather than other animals. The term “herbivorous” comes from the Latin “herba” meaning grass or herb and “vorare” meaning to devour. So herbivorous fish are those that “devour plants.”
In scientific classification, true herbivorous fish are those species that naturally feed on phytoplankton, algae, aquatic plants and weeds as their main food source. Species that occasionally supplement their diet with some plant material but mostly eat insects, smaller fish and other meaty foods are considered omnivorous rather than herbivorous.
Key Characteristics of Herbivorous Fish Species
There are a few key characteristics that set herbivorous fish species apart from other fish:
- Specialized mouth parts and teeth suited for rasping algae and plants
- Long intestinal tracts to aid in the digestion of fibrous plant matter
- A tendency to school in large groups to graze on aquatic vegetation
- Bright coloration in species like parrot fish and surgeonfish
Some popular examples of herbivorous fish groups include:
| Cichlids | Many cichlid species in African rift lakes |
| Livebearers | Swordtails, mollies and platies |
| Loaches | Clown loaches, zebra loaches |
| Plecos | Common pleco, clown pleco |
| Rainbowfish | Threadfin rainbowfish |
Common Freshwater Herbivorous Fish
Cichlids
Cichlids are a diverse family of fish often kept in home aquariums. Several species are herbivores that graze on algae and plant matter. Examples include the convict cichlid (Amatitlania nigrofasciata) and the yellow lab cichlid (Labidochromis caeruleus).
These fish use their specialized teeth to rasp algae off surfaces. Their tall, compact bodies allow them to intricately navigate aquatic vegetation to feed.
Plecostomus
Plecostomus, or plecos, are armored catfish perfect for algae control. Their suckermouths let them scrape film algae off glass, rocks, driftwood, and other surfaces. Common plecos (Hypostomus plecostomus) can grow over 2 feet long while bristlenose plecos (Ancistrus species) stay under 6 inches.
Though omnivores, plecos thrive on herbivorous fare like vegetables and algae wafers.
Goldfish
Goldfish are versatile feeders that shift between herbivory and omnivory depending on resources. Common feeder goldfish (Carassius auratus) and fancy varieties like fantails will graze freely on plants and algae. Their motile lips allow them to tug and nibble vegetation.
Offering greens like spinach and blanched peas supplements their diet. Goldfish enjoy grazing levels of protein too from live or freeze-dried treats. Their dietary flexibility suits them well to planted aquariums.
Tetras
While most tetras are omnivores, select species specialize in herbivory. The marbled hatchetfish (Carnegiella strigata) filters fine organic particles from the water column. Its upturned mouth makes it adept at catching drifting plant matter and algae.
Another unique tetra is the silver tip (Hasemania nana), a long-bodied fish that feeds heavily on aquatic plants using specialized guts. Offering sinking algae wafers and blanched vegetables will sustain these unique tetras.
The Role of Herbivores in Freshwater Ecosystems
Impacts on Algae Growth and Plant Life
Herbivorous fish play a crucial role in freshwater ecosystems by keeping algae and aquatic plant growth in check. Common freshwater herbivores like goldfish, cichlids, and catfish graze on algae and vegetation, preventing excessive growth.
Uncontrolled algae blooms can be detrimental, blocking sunlight, decreasing oxygen levels, and releasing toxins.
Herbivorous fish exert top-down control on primary production, keeping the system balanced. By feeding on detritus and periphyton, they recycle nutrients back into the food web. Their grazing also increases plant species diversity and clears space for new growth.
Effects on Water Quality
The feeding activities of herbivorous fish can greatly impact water quality. As they uproot aquatic plants and stir up bottom sediments, nutrients get released into the water column. This leads to some turbidity but also benefits phytoplankton growth.
Additionally, their waste products help fertilize aquatic vegetation and algae. The right balance between grazing and nutrient replenishment helps maintain good water quality and clarity.
Place in Food Chain
As primary consumers, herbivorous fish form an essential link in freshwater food chains. They transfer energy and nutrients from aquatic plants and algae to predatory fish species higher up the chain. This energy transfer across trophic levels helps sustain entire freshwater ecosystems.
Young fish and fry also depend heavily on herbivore species as a key food source. By grazing on vegetation, detritus and small invertebrates, herbivores incorporate energy and nutrients into their tissues which then get passed upwards to their predators.
Keeping Herbivorous Fish in Home Aquariums
Tank Size and Setup
When keeping herbivorous fish like plecos and silver dollars, bigger is always better. These fish need plenty of swimming room and appreciate larger tanks if possible. For a small group of 3-5 herbivorous fish, aim for at least a 55-gallon tank.
The more fish or larger the fish, the bigger tank you’ll need. Make sure the tank has strong filtration to handle the increased bio-load.
The tank setup should include plenty of hiding spots and shaded areas. Add rock caves, driftwood, and dense plants to help herbivorous fish feel secure. Using a dark substrate can also make them feel more comfortable. Maintain water quality by performing regular partial water changes.
Compatible Tank Mates
Many schools of small tetras or rasboras make great herbivorous fish tank mates. Avoid keeping them with aggressive species that might nip at long fins. Bottom-dwellers like Cory catfish are nice additions that won’t compete for food or space.
If keeping multiple plecos or herbivorous fish species, introduce them to the tank all at once while young to avoid territorial disputes. Be mindful not to overstock the tank and always research fully-grown sizes to prevent issues down the road.
Ideal Water Conditions
Most herbivorous aquarium fish thrive in relatively neutral water between pH 6.5-7.5. Water hardness varies from soft to moderately hard depending on species. Do research to determine specific needs.
Consistent water temperature around 75-80°F tends to keep herbivores happy and healthy. Investing in a reliable heater and thermometer helps maintain a stable environment.
Good oxygenation via air stones or powerheads provides necessary surface agitation. Strong water flow also prevents debris accumulation that can quickly foul a heavily stocked tank.
Appropriate Plants and Decor
Live aquarium plants offer excellent nutrition for herbivorous fish while aiding water quality. Choose hardy plant varieties like anubias, java fern, crypts, vallisneria, mosses, and anacharis. Steer clear of delicate stems that may get uprooted.
In addition to plants, add natural woods, rocks, and smooth river stones to mimic the fish’s native habitat. Choose sinking algae wafers and spirulina pellets as supplemental foods if needed. With good tank maintenance and diet, herbivores make wonderfully unique additions!
Breeding Herbivorous Species
Mating Behaviors
When it comes to mating behaviors, herbivorous fish exhibit some fascinating rituals. Many species engage in elaborate courtship displays to attract a mate. For example, male Siamese fighting fish flare their fins and swim in circles around the female to show off their vibrant colors.
Cichlids often perform mating dances, quivering their bodies and fins to catch the female’s attention. Another interesting behavior seen in characins like tetras is grouping spawning, where several males and females come together in a frenzied mating ritual.
In preparation for spawning, pairs or groups of fish will clean off surfaces like leaves or rocks to serve as a breeding ground. Some species even construct bubble nests, like the dwarf gourami. Parental care is common among herbivorous fish, with parents diligently guarding eggs and sometimes even protecting hatched fry in their mouths!
Spawning Habits
The spawning habits of herbivorous fish are well-adapted to their plant-based diets. Many species scatter eggs over vegetation, where phytoplankton and algae provide an abundant first food source for hatchlings.
Live-bearers like mollies and platies give birth to free-swimming young that can immediately forage on plant material.
Most herbivores spawn multiple times in a season, producing dozens to hundreds of eggs. This helps offset losses from predation and environmental factors. Spawning is triggered by changes in water chemistry, temperature shifts, or light cycles.
For example, rainbowfish spawn at the start of the wet season in their native Australia when water temperatures rise.
Herbivores utilize a range of clever spawning strategies. Some cichlids are mouthbrooders, with parents incubating eggs in their mouth for protection. Others spawn in muddy hollows or secreted underground chambers. Male seahorses even have a pouch to carry developing young!
Raising Fry
Raising the vulnerable fry of herbivorous fish requires some specialized care. Infusoria, microorganisms that grow on plants, make an excellent first food due to their tiny size. Newly hatched brine shrimp and microworms are also perfect for nourishing fry.
Fry should be kept in a separate tank with gentle filtration and warmer temperatures around 78-82°F. Java moss makes a great shelter for fry and helps oxygenate the water. Hornwort and elodea are also excellent choices since they provide infusoria and areas for fry to hide from aggressive tankmates.
Partial water changes of 10-20% should be performed frequently on fry tanks, using appropriately diluted dechlorinated water. As fry grow, they can be weaned onto crushed flakes, then small pellets and algae wafers. With attentive care, most herbivorous species can be raised to adulthood.
Conclusion
Herbivorous freshwater fish like cichlids and plecos are fascinating creatures that are vital components of lake and river ecosystems. Their plant-based diets and behaviors have ripple effects throughout the entire food web.
Many herbivorous fish also make excellent additions to home aquariums when provided with ample vegetation and water conditions that meet their needs.
We’ve only scratched the surface of this complex topic here. To recap, we defined what makes a fish herbivorous, highlighted popular herbivorous fish species, discussed their ecological roles, explained how to care for them in captivity, and covered some breeding basics.
I hope this overview left you with a greater appreciation for the plant-eaters of the freshwater world!
