fertilizer

What have you had success with? I will have low tech , mostly water column feeders, some root feeders. I will be using black sand for substrate.u

I've been using Seachem Flourish and Excel in my planted tanks with some success but I noticed that the Flourish gets dark over time. I'm assuming that this is due to oxidation of the nutrients inside. If I get the little bottle, I use it up before it gets really dark. So here's my question -...