Most fish are omnivores, eating whatever aquatic bugs, algae and other things that they find. Loaches generally eat off the bottom, searching through the substrate for snails, worms, crustaceans and other animals.
In aquariums they like a rotation of foods, including vegetables, frozen foods and others.
I feed my fish a very wide range of food. What one fish may not eat another does, so that over the course of a week all the fish have a chance to turn their nose up at something.
Dried foods, flakes, pellets or wafers:
Read the ingredients. You want a lot of whole fish and shellfish, spirulina algae and little or no fish meal or grains. I have found New Life Spectrum and Omega One to be very good, and have recently ordered foods from Almost Natural Tropical Fish Food:
www.antff.com Very fast service, and quality products. All the ingredients are not listed at the site, but the blends are made from whole fish and shellfish.
Frozen foods: Bloodworms, Daphnia, Tubifex, Brine Shrimp and more.
Fresh or frozen vegies, cooked until they are tender-firm, not overdone 'til they turn to mush:
Peas (remove skin)
Green Beans (slice into thins strips)
Zucchini and other summer squashes
Butternut Squash, Pumpkin, Yam: Bake 'til tender. Boiling is OK, but it gets mushier.
Cucumber, Oranges, Melon and other fruits: Fresh, sliced thin.
I also make my own frozen food from whatever fish is on special at the grocery store. There is a great recipe here at Loaches. Probably at the top of the Fish Health Forum.
Yes, it is there. My computer is acting weird, or I would link it for you.
38 tanks, 2 ponds over 4000 liters of water to keep clean and fresh.
Happy fish keeping!