I was actually wondering myself the same question in regards to running both Phosban and Carbon in the same reactor and emailed TLF and they replied with this:
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From: Sales and Support <info@twolittlefishies.com>
To: Cristian Albu <longin.albu@yahoo.com>
Sent: Friday, March 9, 2012 12:41:01 PM
Subject: Re: PhosBan 150
Dear Christian,
For a 34 gallon tank you only need one reactor, not two.
You can mix the carbon and PhosBan in the same reactor. We recommend our HydroCarbon2 for this purpose because it does not leach any phosphate.
Your proposed pump arrangement is not good. This is best done with the reactor hanging on the back. If you tried it the way you proposed it would be difficult to service the reactor and you would have a high probability of a leak. I believe you can fit the reactor in the chamber where the denitrator is optionally located. I don't know whether the back area cover can accommodate the reactor fittings however.
Sincerely,
Tech Support
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