Cycling of the tank is necessary to raise goldfish or any other
fish. The term cycling is refering to "Nitrogen Cycle" and in this page
I will get into detail about the whole thing in simple terms.
We recommend that when setting up new aquariums, a fishless cycle should be the first choice. Please see this link. However, if you have already added fish, then you will need to do a fish-in cycle, which is discussed further below.
Okay lets start with the basics. Goldfish need at least 20 gallons of water. So you've got a 20 gallon tank and you just got the tank home with no fish at all at this point. Well the first thing is to set the tank up. In short terms setting up the tank is placing water into the tank, rocks, filter, dechlorinator and plants if you want to. Now once the tank is all put together you will need to let the tank run for atleast 24 hours before adding the fish.
After 24 hours of running with the filter in the tank, you will need a fish that will help cycle the tank. I wouldn't get your goldfish right now, there are Danio's that are very hardy fish and they can take they cycling of the tank better than the goldfish can. After you add the fish in to the tank I would strongly suggest getting a test kit so that you can see the levels of ammonia, nitrites and nitrates in the water. This is going to be the only way for you to find out if its safe for you to add the goldfish to this tank.
Okay, so now the fish is in the tank and your wondering whats next.......Well now we get into the cycling of the tank. The cycling of the tank is simple but can be complicated. So I'm going to try to make it easy to understand.
The first thing that's going to happen to the tank is the ammonia is going to get very high, this is caused by the fish waste (food, plant decay). You will need to test this, because if the levels get to high the fish can die of ammonia poisoning (blood poisoning). You will need to make sure that the level stays below the 1.0 mark on the test kit. The way to help this level if it gets to high is small water changes every day of at least 20-30% this will help to relieve the ammonia level off of the fish.
The ammonia level will rise until about the 10th day, the nitrites will kick in around the 10th day also. Nitrites can be just as dangerous as the ammonia levels. Nitrite bacteria basically convert the ammonia into nitrites. If the level of nitrites gets above the 1.0 mark on the test kits you can get Nitrite poisoning (fin rot, flashing, bacterial ulcers etc.). This level can be controlled to by small water changes of 20-30% when you test the water. It is very important that you test the tank at this level, as most fish that show signs of stress will die at this level.
After about 20 days the next level of the cycling will happen: Nitrates. This is not harmful like the others. It can be if the levels are very high in the 100 range. Once the ammonia and nitrite levels are down to 0 and you just have nitrates the tank is fully cycled. The only other thing that you will need to do now is regular water changes. Now you can add your goldfish.
One thing to remember, tanks at temps 78*f will cycle in about 30 days, tanks with lower temps will take much longer to cycle.
Cycling with Goldfish
Some of you will most likely be finding out about cycling after youve already added your goldfish to the tank and noticed a few odd things like cloudy water or erratic behavior. The rest of this section will help you through the cycling with your goldfish still in the tank.
By now, you've discovered that your filter does quite a bit more than just clean out the bits of poo and uneaten food. Despite the complexities of all that is going on in your new tank, there is a simplistic format to help you nurse your new goldfish through it all.
First, you'll need to get the ammonia under .50 ppm and the nitrItes under .25 ppm by performing water changes. These (and all water changes) should be done with temperature and Ph matched dechlorinated water.
Now, test your water every morning and night. If the ammonia climbs higher than .50 ppm, do a 50-80% water change. If the nitrite gets over .25 ppm, do a 50-80% water change. These levels will rise daily and closely monitoring them is very important. You'll need to keep this up for close to a month from the time you set the tank up. Sometime between 21 days and 30 days, the tank should be very nearly cycled, although some tanks can take longer. Your tank should be fully cycled when the ammonia and nitrites are no longer registering on the kits (0ppm). Ammonia will be the first to disappear, then a week or two after that, the nitrItes will begin to disappear. It's about that time that you should start seeing nitrAtes appear on the kits. This is when you'll be nearing the end of your water changing vigil. After the tank has become cycled, you only need to do weekly water changes of 50-80% to keep the nitrates to a safe minimum (40ppm or less).
Salting for nitrites:
Aquarium salt will help your goldfish deal with the nitrites that will invariably be hanging out in your tanks water for a while. As you read above, the nitrites will hamper your goldfish from receiving enough oxygen to their bloodstream. Salt will act as a buffer and make life a lot easier for them. Its important to remember that salt cannot be filtered out, or evaporate from the water. The only way to remove it is to do water changes without it. That is why extra care must be given to the amount that you're putting in.
You can add aquarium salt to the tune of 2 1/2 level teaspoons per us gallon. At first, you'll want to bring them to this level slowly. The best way to do this is to get the ammonia to 0ppm or less and the nitrites to .25 ppm or less, then you can start adding salt. You can continue to add salt until the tests register 0 for nitrites (up to 30 days with tank temp in the upper 70's). The initial addition of salt should be split up into three additions if water changes are more than 50% a day. If they are somewhat minimal, you can begin adding the 2 1/2 teaspoons per gallon to the gallonage that you're adding back to the tank. Basically, you are trying to make the salinity rise somewhat slowly so as not to stress your goldfish even further.
symptoms of toxic exposure:
During this toxic and stressful time, your goldfish may display a wide variety of symptoms. Black spots can appear. They are signs of ammonia burn and actually signify healing. Tails and fins might begin to look ragged, torn or split. Red veins in the tail. Fins clamped, bottom/top sitting and gasping for air are all symptoms as well. These symptoms are all known to get better once the params have been brought to a manageable level and/or a cycled tank has been achieved. However, sometimes these and other symptoms will persist beyond that. It is wholly advisable to get the tank fully cycled and under control before any treatments are administered.
Another way to Cycle the tank is Fishless Cycle.