I wouldn't say it's a sharp learning curve, but more of a long, extended, very extended learning curve. We're all still learning every day.
Spend enough time changing the doses of various elements and you'll start to visually be aware of what affects what. Phosphorus in my tank creates a lot of stem growth but also boosts green algae; iron clearly makes red plants glow; potassium increases leaf growth and health; etc. No tank is alike, so your dosing will always be "specific". At best, we can give you suggested, average doses. It's up to you to see how your tank responds. I haven't been dosing as much Excel as these guys and my plant growth hasn't been affected, tho I do have a bit more algae than I'd like. I've been ramping it up to use the rest of my bottle before my glut is delivered. As I up my other ferts and finding my liquid stuff is consumed much faster than expected, that too is getting replaced with a PPS Pro pack.
Lighting is something I planned from the get go. Once you have what you want visually, everything else should follow suit.
I look at it in a similar way to exercising. If your goal is to be the biggest guy in the gym, you're not going to reach that goal just doing any one thing. Calories, protein, sleep, etc, etc. If you're juicing your plants with light they're going to need the nutrients to compliment it. Keep at it and you'll quickly be at a point where you wish you had a bigger tank. I know I am.
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