I bought the 306 first for a 45G tank. For a new tank much larger I needed a lot more, so I bought two SunSun 404B's. Have received them, tested, but not installed.
The 306 is a delight -- easy to maintain (contrary to what people say), quiet, etc. HOWEVER, two months in my flow is about half what it was -- I've cleaned the media, I've cleaned the impeller. I found the impeller cover warped and replaced it (actually Fluval sent me a new one), I reduced the amount of media, replced the floss (both), removed the carbon entirely. Still significantly reduced flow, to the point I worry if I'm getting enough surface agitation. I have no idea what is wrong.
So that's why instead of (say) a Fluval FX6, I decided to try the SunSun.
The SunSun's are what I expected -- basic, simple, nothing fancy, and cheap. The only problem so far is that their flow is low also -- these I measured in a sink, with NO media, at 278 GPH
. But by eyeball comparison it's still twice the 306 (now).
Makes me wonder if all the manufacturers just lie about their flow rate.
If it wasn't so much trouble (since I'm depending on the bacteria in it) I'd measure the Fluval. Maybe next water change. I'm guessing I'm getting 150 GPM or less.
Anyway... so far I've found no issues with the SunSun (other than flow, which also is an issue with Fluval). Basic, Simple, Cheap. Easy to open, primes OK, LOTS AND LOTS of media space (though it came with practically nothing, just some floss pads).