[whatcaneyedo]

Some people have problems with the Tunze Osmolator pumps from time to time but I've been using one for a few years and never had an issue with it. They're a great system in my opinion. There are also plenty of threads on this site about ATO systems so do a search and decide for yourself if a Tunze is right for you or if you want to save some money and do something simpler.

The larger your freshwater container the less often you'll have to top it off... thats the only difference I can think of.

There is no reason to have a circulation pump in your freshwater container.