I would let the percentages dictate your actions. If you've got leathers at 5% of total final stocking then I wouldn't worry so much. If you've got a lot of leathers and it might be 40-60% of your final stocking then I'd say thin the herd. It really all depends on your priorities. If you really like the look of the leathers (and you want a lot of them) then your
SPS will suffer and that will be ok because you favor the leathers. If you really like the look of
SPS then keep your leathers to a minimum. If you want the flow-y-ness of the leathers without the poison then go with the
LPS.
I don't think it correct to tell you "with the size of your tank you'll be fine" because at some point you'll have a fully stocked tank even for its size. If you get there and your percentages favor the leathers then you'll have problems no matter. I'm not sure how much carbon it would take (nor how often you'd need to change it) in order to keep the toxins at levels that wouldn't adversely affect your
SPS; I don't think anyone can tell you that. You won't know until you're asking questions 3 years down the road about why this and why that...
Most people really serious about
SPS wouldn't put anything else in the tank (
shrooms, zoos, leathers...) because at some point the zoos will take over and grow right up the skeletins of the
SPS, killing everything in their path. Same thing with
shrooms, really. That's not so practical in a tank that size but it might help you to keep things in zones. Zones don't help with the leather toxins, but keeping their numbers down will.
I keep one leather in my 120 (320g water volume). The rest of the tank is
SPS or
LPS. My 65 (with its own water system totaling 75g) is heavy with leathers and
shrooms and
LPS. Each tank has its own personality.
