Read build threads here, you can just build it yourself. 550 gallon tank, a sump with K1, Eheim 2262 in the mix. looks like he has a drain in the side of the sump with a short elbow to drain it--looks a lot like an auto water changer to me. He has a valve on it that's closed, for some reason, though.
Big fish and some rays. Lotta guys on here doing that. K1 conversations going on all the time.