CichlidFish.com - Fish That Think.

We bought a xp1 and I can get the xp3 for about $20 more. We paid $99.95 for the xp1. We have a 50 gallon and someone said that it wouldn't be a bad idea to go and take the xp1 back and get the xp3? I realize that the xp1 is for up to 45 gallons. and then when I told my SO that the xp3 is for up to 175 he say's we will never have a 175 gallon tank so he doesn't quite understand. Should I get the xp3 since it's on sale and will it keep the tank cleaner then the xp1?

Depends on what type of fish you have. But I am a beliver, in the bigger the better for filters. Less tank cleaning ect. I think for the extra 20 dollars, I would go with the xp3.
Just for the info, O's are petty dirty fish, and require a great tank volume turn over, to keep the water clean. Since most filters also double on the biological filtration, you need to move the tank volume through the filter about 10x the tank volome per hour.
IE 45 gallon tank, filter rate should be 450 gallons per hour. For your 50 you will need a 500 gph filter for most chilid type fish. These gph rates will keep the water very clear, and keep the nitrifying cycle working properly.