A lot of fish species need vegetable matters to thrive. Keep in mind that even carnivore species normally ingest small amounts of vegetable matter (primarily algae and plant leaves) in their natural environment. If you keep them in a barren aquarium without plants and algae and feed them carnivore food only they can develop nutritional deficiencies over time. When it comes to omnivore and herbivore fish, most of them love to be given vegetables. Vegetables are not only valuable for their nutritional content; they can also prevent constipation in fish since they contain a lot of fibres.
If you want to give your fish vegetables, you can for instance start out with zucchini since this is a favourite food among many species, including a lot of livebearers. Slice a few medallions off a zucchini and place them in boiling water until they become soft. You can also place the medallions in the microwave. Wait for the veggie to cool off. The zucchini is now ready to be served to hungry fish.
Tips! If you do not want to prepare zucchini every day for your fish, you can slice an entire zucchini into medallions and boil it. Place the medallions on plastic wrap on a cookie sheet and put it in the freezer. When the zucchini slices are frozen, store them in a plastic bag in the freezer. When it is feeding time, simply take out one slice and thaw it.
Some types of vegetables can be served raw or after being put on the hot running water for 30 seconds. Koi, goldfish and a lot of marine herbivores are for instance known to love raw or ‘blanched’ romaine lettuce, beet tops and swiss chard.
If you fish are prone to constipation, try giving them boiled green peas. A lot of goldfish breeders regularly feed their fish boiled green peas since the compressed and heavily altered goldfish has compressed intestines that easily clog up without sufficient amounts of fibre. Boiled green peas have saved the life of many a goldfish. Boiled snow peas are also popular but should be split prior to serving.
If you keep Plecos, you should definitely pick up some broccoli the next time you go to the supermarket. The dark green parts of the broccoli can be messy to use, so most aquarists use only the pale green stem pieces. Boil the broccoli and leave it to cool. Cut loose the stem pieces and serve. Your Plecos will love it!
Last but not least, if you keep decorative snails and want to feed them something more than algae you can boil some green beans and split them before placing them in the aquarium. Green beans are a favourite among a lot of snail species. If you have a lot of small ugly snails that you want to get rid of, you can place a lot of green beans in the aquarium and pick them up when they have been filled with hungry snails.