They work do a degree BUT... IMHO
I would find out why you have a NitrAte issue and maybe up your water changes. I have an issue with NitrAtes and found that my 25% weekly's weren't enough so now I'm doing 50% wc
and that is holding.
"When creating an aqua scape, strive for the beauty of imperfection, as its art and there is no wrong or right, it's left open for interpretation" James Findley