I ran two emp 400's and a Xp3 on my 75 for 4 months, worked very well, removed the canister and ran them for 2 months more untill getting a wet/dry. The emps worked like champs. I also run two 29 gals with one emp 400 in each and the water couldn't be better except for the microbubbles.
The only gripe I have is they made a crap load of noise for the first few days from the impeller rattling, after that they quieted up for the most part.
Every once in awhile one of them will start up again, pulling the tube up and down or cleaning the housing out tends to fix it.
I've only had to replace the mechanical media on them once in 6 months, fairly good value IMO.