Well if the pump is used as a submesible pump, (under the water), then all that heat will go into the water, 100% of it; however, if you are using the pump inline, (water in tube/water out tube), then not all of the heat will end up in the water, some will go into the surrounding air. But, logically it would make sense that even in an inline setup, there would be an increase proportional to 28:50, although that may not amount to very much, if you want an idea, leave your current pump on, and feel how hot it gets, then you'll have an idea of how much heat is going into the air rather than the water (inline). Obviously more heat will come from the 50w, but the actual increase in the water temperature might be almost negligable.
But if anyone has any specific experience with this, we're all ears
