I have put water from an established tank into the system twice since I got it up and running. Unfortuneately, due to time and spacing constraints, I had to get the animals in there before the tanks were fully cycled. The biofilter does seem to be working in some capacity as it is. Do you think it would help to add additional water from the established tank? I don't really ahve a choice in keeping the octos anywhere else. The tank is a 40 gallon, I'm pretty sure. It's the biggest we had. I have 2 40 gallons hooked up to a sump, each on separate pumps. The bio filter is in the sump, and I have a UV filter as well. each tank has their own up to 50gal fileter with activated carbon and filter sponge. The ammonia did go down after a bit so the biofilter seems to be working in some capacity.
I talked with some people here at the school, and they said they didn't think it was the ammonia. The change wasn't really gradual either. They were feeding fine, then all of a sudden there was an appetite drop the next day...then all of a sudden a while later one would stop eating and soon afterwards die. The one that died didn't even want to attack a crab in the end. I was told ammonia would be a less gradual, more visible change with a quick reaction or death as the case may be. This has been over a period of 3-4 months.