18. Why is my fish floating?
Read the section on swimbladder problems. There are a lot of potential causes. I would say the most common is the overfeeding of dry food, causing impactions in the gut. Interestingly, water quality problems often seem to be a factor as well. If you keep a fish with floating problems in very clean water (not "clear" clean! As in "frequently changed") it can help a lot.
19. Why can't my fish get off the bottom?
Usually this is due to a fish being near death from illness. If the fish is listless, drifting, cant maintain its balance, and/or isnt eating, it is very likely ill. Four out of five notes I receive with this problem have severe water quality problems, usually during the initial period of cycling the tank (developing cultures of good bacteria that oxidize fish wastes, in a process called "biofiltration"). For this case, you need to get your act together on determining your water quality and doing enough water changes.
To help this specific fish (you probably cant), get a five gallon bucket and some uniodized table salt (see question 23). Fill the bucket with dechlorinated water that is the same temperature as the tank water. Dissolve one tablespoon of salt per gallon in the bucket. Put the fish in the bucket. Then empty the tank, refill with dechlorinated water, and put one tablespoon per gallon of salt in. After 8 hours, move the fish back to the tank. Then do 50% daily changes with salted water for a 10 gallon or larger tank. For a smaller tank, repeat the bucket/tank transfer routine daily. Do this until the fish is better or dead.
Sometimes a goldfish develops (or is born with) a physiological problem that prevents it from controlling its buoyancy, resulting in either floating (most common) or sinking. These fish are usually otherwise healthy. They can live like this for a long time, though they tend to get lazy and just sit in corners waiting to be fed. Not much that can be done. Sometimes exercise (like living in a pond) or seasonal temperature changes help.
20. Why is my fish listless and not eating?
With goldfish, eating is usually the last thing they stop doing when sick. So a non-eating goldfish is probably a very sick goldfish.
Make sure your water quality is very good (other questions explain what this means). If you keep the fish in very healthy conditions, there is always a chance it will recover. I particularly like using salt in the water, at one tablespoon of uniodized salt per gallon. This will slow down external parasites and some diseases, as well as minimizing the stress from water quality problems and promoting rapid healing.
Based on the symptoms of "listless and not eating" I cant give any better or more specific advice than this.
21. My fish has white spots on it. Is it sick?
If the spots are small specks distributed over its body and fins, the answer is yes. It has a parasitic disease popularly called "Ick". Go to the links section of this web site for links to sites with health information to find out more. There are a number of over-the-counter medicines that work quite well for Ick. QuickCure is a good one. Follow the instructions.
However: if the spots are only on the front rays of the two pectoral fins and on the gill covers, your fish isnt sick. It is a male goldfish in breeding condition! These are called breeding tubercles and look almost like white sand stuck to the fish.
22. My fish has just developed red streaks in its fins or red veiny areas on its body or black areas on its fins. What is wrong?
In a new tank, these are all classic signs of an outrageously high ammonia level. Start changing water big time. 50% two times per day is a good starting point. And add salt to the water; one tablespoon of uniodized salt for every 5 gallons.
The black areas are actually scabs that form on severely irritated tissue. They should disappear in a week, with proper care.
In a well established tank, it is harder to say what is causing these symptoms. Could be something really nasty like an outbreak of aeromonas or viral septicemia. But in my experience the problem for me has always been a contaminant in the water or a surprise failure of the biofiltration. Iron oxide, falling off rusting fluorescent shop light reflectors, is my classic problem.
23. You say to use salt to treat just about everything. What kind of salt? How much?
If you can find kosher or pickling salt with nothing added to it, that is perfect. Uniodized table salt that does not use Yellow Prussate of Soda as an anticaking agent is fine. I personally use water softener salt ("Solar Salt" from Cargill) which runs me about $4 for 40 pounds.
The "aquarium salt" sold in pet shops is of course fine, but expensive. However, DO NOT use sea salt or marine salt intended for salt-water aquariums. This has a lot of minerals in it besides salt and can significantly change the pH of your tank water. Plus it is outrageously expensive.
Amounts: I do not routinely add salt to my tanks, but those who do seem to like one tablespoon per five gallons of water as a consistent level. Goldfish can stay in any concentration up to and including about a tablespoon per gallon pretty much indefinitely. For quarantine and disease treatment, I usually use this top end one tablespoon per gallon figure.
There are also high concentration salt dips recommended for new fish, prior to quarantine, to kill external parasites. I have no experience with this, so you will have to look elsewhere for recommendations.