it will depend on its size (the total litre capacity), how many fish there are, and wether it is a cold water or heated aquarium.
It has to be cleaned every so often, mainly if you can see that it is dirty than you should clean it. And it really should be cleaned every 4-5 weeks.
Draperies should generally be cleaned one or two times a year.
THe viewsonic screen should be cleaned as needed,this time will vary on conditions.
There is no set time. It would be cleaned when needed and some may never need it.
If children are going to be using them, you should clean them very often, like once a week. If not then you can get away with cleaning them less often.
every day
You need a gunsmith,
about every 2 weeks
They do not need to be bathed. If they are shedding you should groom them. If they are dirty, then they need to be cleaned. Make sure their cage is kept clean.
== == every day howrse.com answer: Daily
You should clean it every 6 months or so to keep the reading lasers sharp.
Microscope lenses should be cleaned with lens paper before each use. This maximizes the clarity.