Canaries are best fed with a seed mixture of 80% canary grass seed and 20% canola rape seed as their basic diet.  Canary grass seed is light colored and shaped like a football.  Canola rape seed is dark and round. 

These seeds are contained in the pre-mixed bird seed you find at department stores, but these retail packages also have a lot of seeds that canaries don't like.  One "filler" type of seed often used is millet, which the canary will usually throw out.  If you can't find an 80/20 mix, choose a package that is formulated specifically for canaries.

A canary will eat about a teaspoon of bird seed each day.  Canaries husk their seeds, so be watchful of a seed dish that looks full.  It may be covered with empty husks, and the bird may not realize that there is seed under the layer of husks.  Your canary can starve if he can't find his food.  Blow off the layer of husks each day, or better yet, give him a fresh supply of seeds each day. 

There are several special seed mixes that are available to enhance song.  This one contains seeds such as thistle, flax, sesame, hemp and anise. 

Canaries do not need grit in their diet because they shell their seed.  They crack the shell and eat the nut meat, throwing the husk back into the seed cup or onto the ground.  Birds like chickens swallow their seeds whole, so grit is needed in their gizzard to grind the seed and allow for digestions.  The canary digestive system is not like that of a chicken.  No grit is needed and has even been found to cause death when fed by parent birds to small chicks.  So, to repeat....no grit for your canary.

Another really good food option is pelleted canary food.  This is made of ingredients such as wheat, canary grass seed, barley, corn, buckwheat, rice, oats, peas, flax seed, beans, peanuts, almonds, fresh dandelion, chicory, kale, apples, pears, honey, brewers yeast, ground egg shell, etc,  Usually there are also vitamins and minerals added.  The mixture is extruded, making small pellets.  There is no mess from seed shelling as the entire pellet is eaten.  You need to be careful if your bird is not used to eating pellets, as he may not realize that it is edible.  Introduce the pellets and continue to feed your seed diet, reducing the seeds gradually as you see him eating the pellets.  Some breeders feed pellets as the primary food and swear by them.

I keep a dish of pellets in each cage at all times as a supplemental food.  There is no waste, and it gives the birds an option to the standard seed mix.

Although a seed or pellet diet as described above is nutritious, especially when supplemented with treats, giving your canary a good avian vitamin is suggested.  Just like humans, in that it's hard to consume all of our recommended daily allowances of vitamins through our diet alone, it's equally hard to formulate a diet for our canaries that is perfect.  Sprinkling avian vitamin powder on their food will supply the supplements that they need.  If you get a vitamin that goes into the drinking water, be sure to change the water in the drinker daily. 

There are also avian probiotics which contain "good" bacteria that is beneficial to the digestive system of your bird.  It can be mixed into the food you offer or sprinkled on top.  Some folks swear by this additive and many veterinarians recommend it's use, especially after a bird is treated with antibiotics.

If you are interested in breeding canaries, you will need to look into the special dietary needs of not only the parent birds, but the special foods you will need to provide for the parents to feed to the chicks, from hatching up through weaning.  I've found that if I talk to a hundred different breeders, I will hear a hundred different "formulas", each having a plan that works for them. 

Since I work a full time job, I have adapted my feeding plan for chicks to provide a cornbread based soft food in the morning, and in the afternoon when I get home from work, I give them a nestling food with fresh boiled egg in it.  The morning food is very nutritious, but omits the fresh boiled egg that can spoil rapidly.  If the parent birds would feed the chicks food that has soured, it can cause the chicks to become ill or even die.  The "formula" used in my birdroom has been adapted to not only fit my needs, but to also provide the right kind of nutrition to the growing chicks and their hard working parents.

Some of the books and websites I refer you to in the "Good Connections" section have very good recipes for nestling foods and diet plans for breeding pairs.  You'll need to make your own choice as to which plan works for you and your flock.