I thought all of them broke away from X-10 due to frequent failure. I contacted Octopus about the X-10's. I also bought a DC 8 just to see if the Octopus would talk to it. No luck. I called the makers of Octopus and asked them if they planned to come out with something like a DC-8 and they said they never heard of it. I'm still waiting for their reply. As of right now, my Octopus is a $650 pH monitor.
Let me digress for a second here... Lissa, you are asking about the red light. The interface talks in short bursts to the x-10's. So it only turns on for a split second to say what needs to be said, and shuts back off. When you unplug it from the controller, it turns on because it is searching for what it should be saying. There is not a problem with your interface.
As for what Pedro and I are discussing, I'm pretty sure both of us agree with what the other is saying, but something is lost in the typing. All I can say is that the X-10's might work for you. They probably won't. They are highly unreliable and like Pedro, if I didn't have a dedicated circut for it, I would not feel comfortable leaving my tank trusted to X-10's.
Think of it like this:
your X-10's turn on your heater since it is cold. Then your lights kick on. The signal now interferes with the x-10's and now your x-10's can't shut your heater off.
In my situation, my X-10 would turn on my first MH light. Once it turned on this one light, the interference kept the interface from talking to any other X-10's. No other lights came on and it wouldn't shut off the one it turned on in the first place at the end of the day. No temperature controlling, pH, timers... nothing. A $650 pH monitor.