Once every fortnight, depending on how many fish in your tank. However, the filter should be cleaned only twice a year. This is because the 'good bacteria' in the filter would be washed out when cleaning.
Do not use any chemicals in your tank when cleaning. Except Water conditioners or Water agers. They are important and should be used every time you do a water change. Also. When doing a water change, Only take out a quarter of the tanks water
every week
almost every other day. i had one and i left it un clean for 4 days and it stuck to the side of the tank.
Well about 3 times a week but if your tank has algae or the water is clouded then it must be cleaned,or the water must be replaced.
weekly
Once a week :))))) i have experience
every other week
If you arent going to do regular maintenance, keep it to 5 or less godlfish.
you should do a 50% water change every other week
weekly 10 - 20% water changes
Every Second! Gold Fish are Very messy and need a filter to keep them alive. I suggest you put your Goldfish in a pond. Make sure there is more than one, Goldfish have friends just like you and me. Or you could get a 20 gallon tank (the tank has to be big enough so goldfish can grow up to 10 inches long WITH a filter. okay long story short, one inch per fish needs at least a gallon!
I have a 75-gallon tank and clean out about 10 gallons every week. Since yours is an 18 gallon tank, I would start with cleaning it every two weeks by siphoning the substrate and removing and replacing 7 gallons. If your water looks dirty try changing 5 gallons every week. But I think you will be good with the two week option.
You feed it the same amount as any other goldfish which is whatever it can eat in five minutes once a day. Be sure to remove any uneaten food you can to keep the water clean.
You should do partial water changes of around 25% once a week. If nitrates are over 40 ppm you should increase the frequency of the water changes and/or the amount to get it down to safer levels.
You should make sure that its in a clean place but you should clean it every few days
You should clean your Clarinet every time you play in it.
You should clean it everyday that you use it.