I wanted to add my two cents worth. I think I have a unique experience on this issue. I keep 7 different species of anemone in a 110 display. There are around 65-70 individual anemones packed in there. They are coldwater nems. I tend to have them grouped together by species but some are close to each other. I have 5 different ones on the same rock. My painted and christmas anemones touch and cuddle and no problem. But when any other nem is in reach they grab them and instantly begin to devour what ever no matter how big. My white spotted rose will battle at the slightest touch but does not move to get close at all. But my smallest nems are aggregating nems and "walk" around battling by nettleing from a distance. I have felt this first hand when moving nems that were doing this. I was touching neither but felt "stinging" on my fingers as they were between the two nems.Also aggregating nems split like mad and for colonies. and each colony will battle rival colonies in the aquarium. through nettling. Currently for three weeks my white spotted rose has been battling a much smaller aggregating and have a standoff. you can see where the nettling a has curled the tips of the rose but no other ill effects noticed. And with all the fighting occurring there isn't any chemical warfare happening. I don't run a skimmer, I have some mechanical filtration, and a chemi pure bag sitting in a tray at the top of the display. And once a month or so, I do a 30-35 gallon water change. I guess what I am saying is that I dont have near what reef filtration is and don't suffer aleopathy nor does the constant nettling affect even the fish. all of this is coldwater so that is a huge factor. But a different stand point for sure.
I too want to incorporate Either my BTA tank into the same sump or pull out the BTAs put in a mag or two in that tank. I run the outflow directly over a bag of purigen and have carbon and chemi-pure to put in the sump if neccessary. But I am a bit nervous due to my rare find of 2 super healthy gigs. But my first thought is it would be safe for the mags but not sure about the BTA's despite the fact that I switched my BTA sump to the carpet tank the day before putting the gigs in. I imagine there was residual something in there and doesn't look like a problem...yet lol.