Feeding:
Goldfish are cold-blooded, so their rate of metabolism depends on water temperature. Do not feed below 50 degrees Fahrenheit. In Spring, when pond water gets above 55 degrees (sustained and measured in the morning) you may resume feeding. Start off light, with lower protein foods. If you see long fecal trails attached at the anus, or the fish is having trouble staying upright in the water, the fish is probably constipated and feeding should be stopped and/or augmented with live food. There are other treatments for constipation in some of the goldfish books.

Ideal feeding temperatures are between 70 and 75 degrees F., above 85 degrees fish can be stressed and consume less food. While confirmation (a nice plump shape) is desirable in show fish, one should take care not to overfeed as obesity can cause fatty liver disease and other health and environmental problems.

My experience with koi was that several small feeding a day are better than a single large feeding. That mixed with frequent small water changes (better yet is a constant trickle of fresh water) and light tank loads produced the best growth. While I believe this combination would be extremely successful with goldfish, I have opted to select a plan for slower growth to minimize swimming disorders and constipation that some goldfish are prone to.

Young fish should be fed 3-5 times a day with higher protein foods, while older fish can be cut back to 1 to 3 times a day with lower protein foods. Many people use the five minute rule when they feed once a day: an adequate amount is the quantity they will eat in five minutes. I modify that to several feedings of what they will consume in a minute or two. Theoretically at 75 degrees they could consume 2 to 3% of their body weight in food a day, but remember goldfish have no stomach.

I feed Pro-Gold pellets, California Black Worms, veggies and a bit of other Hikari and Nozomi products. The worms/live foods are the mainstay of the diet, but I try to keep things varied. During the winter my fish are kept in heated tanks in a green house and so I feed year around.

Fasting:
Other than very young fish, I tend to fast (not feed) my fish one day a week. Also, I do not feed for a few days before AND after moving them or some other major stressful event in their lives, such as going to shows. This comes from trial and error and learning that it just eliminates more problems than needed.

When I go on vacation I ether put the food in individual baggies for each meal with date marked on the bag (and hide the main container), or if it is a week or less I just don't feed them. Too many times have I come how to cloudy water, an empty fish food container and dying fish because the house sitter thought "they looked hungry."

Environment:
Learn about your fish. Many types of goldfish require specific environments to bring out the best of their breed.

Set up that environment and get going long before you bring the first goldfish home. If your system has a biologic filter it may take several weeks to get it fully functioning. Don’t buy a tank load of fish all at once. Bring one home and let the sytem stabilize before adding more and add more in small increments so as to not shock the filter with sudden heavy loads. Monitor your tank’s chemistry with test kits.

Change water, change water, change water, and the change more water! In Japan many hobbyists keep 2 identical ponds. One with fish and one without and they move the fish frequently from one to the other - always cleaning and completely changing water in the pond the fish just came out of. Aquarists can do the same, set up two tanks and move the fish at least weekly. I opt to clean my tanks weekly and do about a 25% water change. At minimum I would suggest a 10% water change weekly, more often if things get funky.

Use of Harmony, PolyAqua or other de-chorine and heavy metal neutralizing product is suggested. Use of Kordon products such as Amquel or PolyAqua can trick some ammonia test kits (a salicylate-type reagent kit must be used). Do not use these products when methylene blue, acriflavine, or malachite green is being used as drug's performance will be effected.

Quarantine & Handling:
Never lift a fish out of the water with a net! Use the net to guide a fish into a cup or bowl inserted in the water and then lift the cup or bowl out of the water with the fish in it. If you must lift the fish use your well wetted hands, not a net. The longer a fish is out of the water the more stress it is under and the longer it will take to recover. Inexperienced sales clerks in chain stores are the worst for this offense.

Look at the fish in the store before you buy. Do you see little white spots all over the fish? Are there dead fish in the tank, along with fish with sores? These are all signs that you might want to shop elsewhere unless you are willing to learn about fish first aid.