Great choice. I just bought the Fluval Venezia 350. I love it. Replaceing the 205 with the 305 will be fine, the inputs/outputs holes drilled in the 190 and 350 are the same size, so there wont be any flow problems. Setting the timers for the light were a bit tricky, but i got it done. I find it to be a very well built/put together tank. I love every thing about mine.