Chris&Barb, I am sorry to hear about the trouble you are having with your Deltec reactor, but it will not work well with ARM. If you check the Deltec forum on RC(sorry guys), you will see lots of people have not had the best of luck with ARM. Also, you could have trouble getting any help from Doug if the pump is damaged. I have heard of arm getting through the system and into the pump. If that happens, I am not sure he can cover it under a warranty.
The Deltec reactor was meant to use ROWAlith C+. I know some people must have it because we sell it to our distributors. If you switch over to ROWAlith C+, I am sure you will get the results you are looking for.