RO Water Nutrients
First a little background and then my question. I have been having trouble keeping the nitrates down in my tanks. Part of the problem is that my tap water that I use for water changes has high nitrates. So if I do a water change the best result I can ever hope for would be the same level as my tap water which I will never achieve unless I did 100% water changes which are bad and I'm not going to do that. My tanks are all heavily planted, I use CO2, medium to high lighting, Eco-Complete substrate, and dose weekly with flourish excel, and flourish iron.
The plants are growing like crazy and my fish seem to be happy as well for the most part. There are some more sensitive fish I'd like to get and so I picked up an RO unit in a bulk buy of some used aquarium stuff I bought.
I've got the RO unit installed, I've replaced all of the filters and I've got nice 4ppm TDS water coming out into my holding container. Now my understanding is that I need to add back some of the minerals to the water for the best results and to that end I've purchased a bottle of Seachem Equilibrium.
So now I've got a great big tank of nice clean RO water and I'm not sure where to go from here. My question is how do I know how much equilibrium to add back so that my plants don't go into shock and die as well as my fish? I bought a KH GH API test kit, but I'm not sure what I should take into consideration for what my target levels should be.
Any advice on this would be much appreciated.