A number of aquarium species are popular for their algae-eating habits and they’re often very good at their job, clearing the aquarium of suitable food. This means that they must be fed, and a number of options are available to keep them in good condition. In addition to these specialised algae-eaters, a good many fishes have evolved to exploit a diet that includes fruit and vegetation.

A good dry food will ensure all the key nutrients are present and spirulina-based diets are a great staple. Flake or granules will suit browsing fishes such as livebearers and barbs which feed in open water and these can be supplemented with occasional treats such as peas (squeezed from their skin), or even chopped fruit such as grapes or pear which are especially appreciated by large cichlids and Silver dollars.

Algae provides lots of fibre, as well as providing a home for invertebrates in the wild and these insect larvae and molluscs etc can be a key part of the diet of many species that otherwise seem to be vegetarian. It’s a good idea to offer algae-eating fishes a range of frozen foods rich in chitin to duplicate this. As well as the fibre derived from the plant matter itself, grazing fish will often take in appreciable quantities of roughage such as dead wood, or leaf litter and this can be an important ingredient in the food intake of species such as plecs, which will exploit the microscopic animals and plants that dwell within this resource.

There are a number of vegetables (and some fruits) that can be offered to herbivorous and omnivorous fish but do wash thoroughly before adding to the aquarium. Suckermouth catfish and loaches particularly enjoy sweet potato, cucumber, courgette, squash, melon, and these can be cut into chunks and weighed down to the substrate for ease of grazing. Leafy greens such as lettuce and spinach can also be used but bear in mind that these can contain significant amounts of nitrogen from fertilisers, and this can increase nitrate levels when added to the aquarium. Like any food, take care to remove any uneaten residue before it gets that chance to break down. For this reason, it’s best to offer these novel items in moderation until you get a feel for how quickly they will be consumed by your fish.