Many aquarium hobbyists introduce algae eaters, such as plecos and catfish, into their aquariums to help control the growth of algae. While algae eaters subsist mainly on algae and decaying plant matter, in order to be healthy, they require a vegetable supplement to their diet. In addition to offering spirulina flakes or algae wafers, offer your algae eaters fresh vegetables once in a while.
Many algae eaters, especially the Oto catfish, enjoy the occasional slice of zucchini. Before putting the zucchini into the tank, blanch it briefly in hot water to soften the vegetable and to remove any germs or dirt. Sink the piece of zucchini in the tank, after letting it cool completely, placing it somewhere your algae eater will find it quickly. To give your fish the maximum amount of time to enjoy their treat, leave the zucchini in the tank for at least one day but no longer than two.
Many types of fish, not only algae eaters, enjoy the addition of lettuce to their diet. Lettuce is a fairly inexpensive vegetable to come by and most grocery stores sell several varieties. Keep in mind, though, that some varieties, such as iceberg lettuce, have fewer nutrients than such lettuces as romaine or green leaf. Blanch lettuce briefly before placing it in the tank and secure it with a vegetable clip or weigh it down with something so it sits on the bottom of the tank where algae eaters can get to it.
Cooked broccoli is a favorite of many algae eaters, especially the common pleco. Prepare fresh broccoli by boiling it until it is soft but not mushy, then strain it and let it cool completely. Slice the stems of the broccoli and sink them in the tank for your algae eaters to enjoy. You may use the tops of the broccoli if you choose, but it can be quite messy to do so because the tops of broccoli break apart easily once cooked.
Green peas are not only a great vegetable for supplementing the diet of your algae eaters, they also can help to regulate the digestion of your other fish. Goldfish in particular can benefit greatly from the fiber in green peas. Before serving peas to your fish, boil them in water and allow them to cool. If you are using snow peas, you will need to split them after cooking and putting them into the tank.