Originally Posted by spaceyJC
Nice! Do you think I can use the medium sized one for both the 10 gallon and the 20 gallon?
The mid-sized XY180 works great for a 10 gallon, here's how big it is once in the tank: http://i.imgur.com/Qw6Kyca.jpg
Also, here's what to expect from the same filter in a 20 long: http://i.imgur.com/JYzbDrZ.jpg
In this tank, there's a HOB on the other end which is why there's only one. In a grow out 20 long, I would either put one mid-sized on each end or the largest one in the center.