I just bought two new Tunzes. MY other two options were a closed loop on a Mag12 I already have and Seios. I decided that with my new tank, it would be toomuch work to plumb it corerctly for the closed loop. I had a Rio2500 from my EV-120 (stock pump for it at the time). I HATED That thing, it would never restart anytime I pulled the plug or power went off. i would have to dig my finger in the prop, or take the top off and mess with it. What a serious PITA!! With much reading here on the forums, I read that a lot of people reported the same problems with the Seios. Personally, you couldnt pay me to deal with a pump that has that problem. That's why I kicked up double the money for the Tunzes...not 10x as much, but double. So far I really like them, and I feel confident in the product, something I cant say about the Seios based on my previous experience with the Rio product line. Oh yeah, Tunzes are half as tall as the Seios...compactness, another reason to buy.