what is the best memory management app?

i want to keep my phone running at it's best and use the Advanced app killer but not sure if that is the best thing for the phone.  think of how unstable windows becomes when you end several applications using the Task Manager.

I find myself turnign it off and one once a day to try to optimze performance. 

Also what is the minimum internal space that you can have before the performance goes down the tubes?

I'm a strong believer that the OS itself is the best manager of its memory. That comes from my experience using Linux on a number of my PCs both at work and at home.  I am not an advocate of app killers, my belief being if you kill apps prematurely you actually cause more memory problems than you solve. There are some excellent (and convincing) articles available on the subject on line.

The OS, coupled with your good judgement, are the best managers of your Eris's resources IMHO.

last night I uninstallted both the Task Killer and Advanced Task Killer apps and took the advice of just letting the OS manage the memory on its own.  I have to say that today the phone was more responsive all day without any major performance issues and the battery lasted much longer than normal.

I  guess that those task killers did not help my phone after all. 

Also I have foudn that if you update or install many applicaitons, it is always good to turn your phone on and off, like a reboot with a computer, and it runs much better.

Glad to hear it worked out for you.  I stopped using task killer awhile back and my phone immediately performed much better when I left it to do it "thing".   Rebooting is a good tip also.  I did recently go a whole month(on purpose) without reboot, adding/deleting apps, and phone never lagged once.  Just wanted to see what would happen. 

Maybe I  could turn that into my 3rd job....