Danios are omnivorous fish; in the wild, they consume algae, plant matter, small crustaceans, worms and plankton. In captivity, you can mimic this diet with fresh, frozen and dried foods. Fish flakes and algae pellets can serve as a staple diet, but you should create a well-rounded diet with vegetables, greens, insect larvae, worms and shrimp.
Offer fresh or thawed vegetables every few days, removing the uneaten food at the end of the day. You may have to try a few veggies before you determine what your fish prefer, and you may have to try more than once. Just because your fish don't eat the vegetables the first time, it doesn't mean they won't love them the next time. Offer only a slice or two of squash, turnips, sweet potatoes or zucchini for every three to five fish. Or, offer one pea, lima bean, sweet corn kernel or green bean per fish. You will eventually gauge how much your fish will consume so that you don't offer too much food.
If you have greens on hand, offer them raw to your fish. Danios will eat Romaine lettuce, spinach, cabbage and Swiss chard. You can also give them dried seaweed slices. Greens are best fed using feeding clips or magnets, placing a slice or two per magnet.
How to Feed Vegetables to Danios
When feeding fresh vegetables, make sure to wash off any pesticide and waste residue. Offer sweet potatoes, carrots, squash, zucchini and turnips raw, but blanch peas, corn, broccoli and beans. To blanch the vegetables, dunk them in boiling water for a minute or two, drain the water and poor ice over them to stop the cooking process. You don't want to completely cook the food, as cooking can actually remove some of the nutrients, but you want to soften it to make it easier for your fish to eat. You can either drop the vegetables into the tank and let them sink, or you can use a commercial feeding holder to position the food against an aquarium wall. Position the food low, as danios are surface feeders, so you don't want to have the food high on the aquarium wall.
Other Foods to Offer Danios
Vegetables and commercial fish flakes should be a large part of your danio's diet, but you should also offer a meat protein about once a week. You only want to offer what your fish will eat within 5 to 10 minutes so that the food does not collect on the bottom of the tank. Danios will eat brine shrimp, bloodworms, tubifex and daphnia. If you have access to live foods, offer them; otherwise danios will consume dried or frozen foods.