that is a concept I am not caught up on,overflows.
the reason I was wanting to use the 204 to remove the water from the tank and another to return it was becouse I was under the impression that in order to have an overflow you needed holes somwhere in your tank.....mine doesnt so I thought overflow was just not even an option.I figured the best way to get water to the sump and back out was with 2 canisters.
any additional info on how I would set it up like you said would be much appreciated.
also I will mention that if I put the intake tube of the 204 right near the top of the water and the returning 204 died it couldnt possibly take enough water from the 55 to flood the 10 before the water level dropped below the intake,so I dont need to worry about flooding,just burning out the fluval 204's motor,so basicly if one went out they would both go out unless I caught it immediately.
additionaly,if the differance between the two fluvals is very great (which I dont anticipate) I can manually adjust the water levels of either the sump or the 55 from time to time....