Agree with Tom completely - the 404 is no problem for the 40gal, just too much for the 10
You should start out slowly stocking, as mentioned, and I try to think about it like this: If you are taking media out of a 20gal tank to seed a 40gal, for instance, then stock the 40 a bit shy of how the 20 is stocked, so you don't overload your media, and increase slowly over weeks from there.
Think of the seed material as being able to handle a load similar to the tank where it came from, minus a little, since there is more bacteria in the donor tank than just in the filter. Adding slowly gives the bacteria a chance to multiply equal to the increase in ammonia produced.