Goldfish will eat almost anything that looks like it deserves devouring. That means you have to make sure you keep any scraps of food not meant for fish, out of the bowl, tank or pond. One of the common accidents is during feeding time when the person involved happens to have some kind of food scraps on their hands that inevitably get passed into the water when placing in flakes or pellets.
This can have devastating consequences because as you may already know, goldfish are prone to a number of diseases and all it takes is an alien bacterium to enter the water and before you know it you fish could be laying upside down in the tank within a day or two.
Make sure you always sanitize your hands before feeding time. This will prevent any unwanted bacteria from entering your goldfish's environment.
Flakes
Flakes have become a very popular food as for good reason. Most flake products contain the required amount of nutrient levels your fish need on a daily basis. They are also easy to eat and tend to stay surfaced long enough for your fish to consume the whole amount during feeding time.
This is important as with some other types of food that tend to sink to the bottom and rot for days, flakes stay afloat and usually is fully eaten before it has a chance to fall to the bottom of the tank.
One negative about flakes is that sometimes people get carried away when taking a portion to give to their fish. Goldfish don't need a lot of food and on many occasions suffer from diseases closely linked to overeating. Make sure you don't throw in too many flakes. A small finger-full will be enough.
Pellets
Pellets are the second most popular food for goldfish. They also contain the required amount of nutrients your fish need on a daily basis, but unlike flakes that stay afloat and easy to see, pellets tend to sink to the bottom after a while and can sometimes remain hidden and untouched, which will of course cause them to rot, intern creating unwanted bacterium in the water.
This usually means the tank water will become dirtier faster and must be changed more often than if you were feeding your goldfish flakes. It is much easier to determine how much pellet food you should feed your fish. I small finger-full usually results in the same amount of food to be placed in the tank daily.
