I ran a cannister on my old 150gal and when I changed to a sump,I could not believe the difference it made. The tank looks much better without all the heaters,skimmer etc. hanging on the back. The water level does not drop in the main with evapouration, only in the sump. The cannister was a pain to clean and I always spilled water .I have heard cannisters become nitrate factories also, but I never kept it long enough to find out. Bottom line after all my yammering is a sump is way better than a cannister in every way.