I went all out with my planted tank - ADA substrate, £300 CO2 system, ferts etc. Some plants grew lightening fast! I was cutting down amazon swords every week as they were taking over the tank! But, when you add CO2 etc, the importance of getting the triangle equally weighted (Lights ferts and CO2) becomes more tricky. Tiny adjustments here and there. I found that having such a big tank (5 foot), the circulation of water was my biggest issue - i was not spreading the CO2 about as evenly as i'd have liked.
The short story is that my 90L planted tank looked AMAZING, and i didn't use ferts, CO2 or anything....just fish waste! Zero effort = impressive tank. My 360L took constant tweaks, money, tweaks and more money, and although it was looking good ish, i was never happy with it. I sold all my expensive kit and turned it into a basic planted tank.
HOWEVER, look up 'ADA aquariums' on google and you will see the amazing things that can happen if you know what your doing with CO2. I failed at this, but clearly others have huge success and the difference is amazing