From The Aquarium Wiki
Algae pellets are a sinking food ( formed into wafers, discs, or tablets) made of vegetable matter and algae designed for bottom feeding fish or invertebrates.
- Spirulina algae (which are actually cyanobacteria)
- Corn gluten feed
- Corn gluten meal
- Corn distillers dried grains
- Wheat flour
- Molluscs and crustaceans
These pellets are good for fish and invertebrates that need vegetable matter as a key component in their diet.
Some species of pleco require wood in their diet and if you're not providing bogwood or driftwood in your tank then you'll need to ensure your algae pellets have wood (cellulose) in them.