I think you will like the rw8 more than the w25. I recently purchased a rw15 for my 150 and it is working great. Today I ordered rw8 for the other side. Will probably alternate them every hour. These pumps are very powerful so you will probably have to keep the power down to the 1-4 setting. That's what I have on with the rw15 in a 60 in. tank. In fact that's the reason I ordered the rw8 instead of another rw15. By the way Amazon has them for 89.00 with no tax or shipping charge. Also the "else" mode is preset at the highest range, which may be too high for a 45 gal tank, but the wave 1 setting works very well and you ramp the speed up and down to suit your needs.