well, i'm not sure if it is 100% fool proof yet or not, but i have been running a fluval 405 on the new 150g for a few days now. i am pretty much using it as an overflow box and it seems to be working very well. i shut the return pump off every couple of hours to make sure, if the power goes out, that it won't overfill the sump. knock on wood, it hasn't yet.