Because of algae, which is a plant that grows from water you can either change the water, or just wipe the tank with a cloth or something like that.
the fish probably had babies
Yes, if you separate them for 1 week in a tank with a clear divider.
You should clean a fish tank regularly with water changes of at least 50% each week along with cleaning out any waste or uneaten food, and using an algae scrubber to clean the sides
about once a week
You really dont clean a fish but you clean the tank and you clean that about once a week or every other week and you feed a fish everyday
The best time to clean a fish tank is time that is available to you every week for maintenance.It's a good idea to set aside time one day each week (preferably the same day so you never forget) to do at least a 50% water change, and to clean any debris or waste from the tank.
Your fish will be much happier if you change at least 50% of the tank water every week.
yes you can if you clean the tank properly every week
Every week so your fish can feel like their at home.
once or twice a week
No they do not; having gravel or not is really the choice of the fish keeper as far as how they want the tank to look. You can certainly leave it bare bottomed as many goldfish keepers do to give the fish more swimming room and easier time cleaning the debris from the bottom of the tank each week.
no chances are this is not what killed them, it is much more likely to be that she over fed them. fish in a tank should only be fed every other day and should be cleaned out once a week by removing 25% of the tank water.