what is the debate about iron based phosphate removers - and why are they so bad? is it about leaching iron into the water? if thats the case, just get yourself a heliopora (blue coral) as they can extract iron from the water, oxidise it to a blue salt which is deposited into the skeleton a potential theory?! :-?
regarding zeovit and TN, from what ive read TN can happen anywhere from 'extremely quickly' (within a couple of hours) to 'slowly' (over several weeks) it can also happen for a number of factors. i always decided Im going to 'half dose' zeovit (from the recommended amount) and let the system take care of itself, monitoring it as i go of course. however its one thing to learn from reading web sites and hearing others opinions, but IMO best to learn first hand based on your own system, even though it can end up costly! on the contrary, i've read about zeovit tanks with higher alk (similar or even higher than mine) and they seem to be doing fine, so i dont fully read into the equation that 'zeovit + high alk = TN'. but nonetheless i do value the input, thanks.