nutrient filtering

[fuckthisregistering]

hi all, i was wondering if it would be ok to run a small fish tank carbon filter inside my reservoir to help filter out impurites? i have one on the main line but have been battling root disease as of the last 5 months with complete root death after 7 days then the plant just sits in a stasis. also wouldnt this filter out the nutrients i have added and dissolved oxygen levels?

i have been growing for a long time now and this problem has just hit me to a point i dont know what to do except tear everything down a quite. everything is in check this is a large set up ie. temps, timing ect... as i have two rooms one that was vegged in the room in question then bloomed was cut then revegged and now about to be chopped for a harvest in the room beside it.

the two hydro stores have offered nothing that has worked and i forgot to ask them this question last time i was there. thanks