yup alk would be my biggest concern. For nutrients rowaphos has never let me down its really thin small particle and instructions say u can just place it in the felt bag it comes with. But I have mine in brs reactor, very slow tumble in a 65, and super chalice safe, unlike gfo that I have had bad reaction tooYa, again makes me sick thinking about it lol. Dosing Kalk takes a bit of nerve - don't really need it for the Cal/Alk but to stabilize ph swings at night. And if you don't want to watch your chalice grow a millimeter a year or the scoly slowly waste away you have to feed - I do a couple of times a week. So far I've managed the excess nutrients mainly with water changes the day after feeding but recently added a IM reactor for carbon and phosban (reactor is not at all precise enough for a slow GFO tumble). Ill do a write up about that shortly.