Do Planted Tanks Have a Fixed Life Cycle?
I've been maintaining a planted tank for about 8 years. During that time, I've in essence restarted the tank about 3 times, meaning basically pulling out existing plants and restarting with fresh stock.
It seems to me that each time the tank goes through a cycle of plants getting acclimated, sustained growth, declining growth and eventual death. I believe that over time, I've gotten better at maintaining the sustained growth period but eventually things just seem to stop growing.
Over time I've gotten more sophisticated in my maintenance, to the point where now I have pressurized CO2 from the Fluval 88G disposable cartridges, daily fertilizer dosing using the PPS Pro method and Greenleaf Aquarium fertz.
My substrate has always been gravel. Twice I've added laterite to it, once when it was first set up and about 1.5 years ago when I had to break the tank down completely to move it.
Knowing that the substrate is inert, I do add root tabs for the strong root feeders. I have a Crypt and a Sword. The Crypt is the one plant that I've been able to hang onto for the long haul (it's about 6 years old, at least). My Sword right now is about 4 months old but has taken over the tank.
I find that it's primarily the stem plants that eventually die off but I've had other seemingly healthy swords and Vallisneria die off on my too.
I've been running CO2 and daily ferts, along with regular root tabs for the root feeders for about 3 months now and I'd say the tank is the best its ever looked, but is my success destined to be short lived? Will my plants eventually start dying off again?
I'm wondering if this is just inevitable for aquarium plants. Maybe some species just aren't supposed to live for years and years, or maybe I'm not maintaining them properly.
What are other peoples' experiences with tank life cycles?