I have a couple more questions out of curiosity:
1) When you do the backflush does it impact your bio capacity and cause mini-cycles? I think some folks complained about this.
2) Do think there is a need to run two for backup and sustainability?
3) Are you running drips on your tank? I think you were taking approach of letting your drip fill the tanks up after backwash but dont' remember.
I was under the impression it you would need to backwash more often, which is awesome.
1) I have an Apex on the tank and can see the impacts of backwashes. There is no mini cycle at all. Nothing that has shown on a test kit.
2) I wanted redundancy because I travel often for work and want to make sure I have a heavy bioload capable backup. The more research I did the more I was convinced running two would solve all of the problems people encounter with Ultimas. I can confirm it did resolve all of my concerns.
3) Yes I am running a heated and dechlorinated drip system. Initially I designed the system to let the drip fill it back up overnight. I actually haven't tested this yet. I lose about 30% tank volume for a really good backwash. Since there are pups in the nursery I haven't wanted to push it.
I thought I would have to backwash much more often too. This was a REALLY welcome surprise. I think running two made all the difference in the world. Most people who are running these only invest in one and overdo the flow rate.