Minimum bandwidth guarantee

Is it possible to magically limit and unlimit upload and download speeds depending on network traffic.
Our office has a 200x20mbps connection, but when a couple people launch a large download for an OS update or something, it slams the bandwidth. Right now I have queues setup to limit the bandwidth to 18mbs, but it’s not a real solution if say 10 people were to go full speed. Is this clear?

You can try PCQ as the queue type to more evenly spread things around.
http://wiki.mikrotik.com/wiki/Manual:Queues_-_PCQ_Examples

So I set it up using this awesome article :

http://agratitudesign.blogspot.com/2013/05/bandwidth-management-using-mikrotik.html

(I like using winbox so that I can easily train people underneath me if changes need to happen.)

I just want to make sure of one thing, it AUTOMAGICALLY balances everyone? The article makes no mention of minimum or maximum bandwidths…

It depends on how you have the pcq setup. You can have it where it sets a hard limit on everyone, or set it so that if only one person is using it, they get everything, and are only cut back when others need bandwidth.

http://wiki.mikrotik.com/wiki/Manual:Queues_-_PCQ#PCQ_Rate_Examples

It also depends on how you want to classify the connections how it can or will chunk up the bandwidth.