I've had fish, both fresh and salt, in ponds, aquariums and reef tanks with considerable success - except for the reef. We won't get into that here.
Right now I have a 20 gal, Damsel only tank, that has been an experiment for me for the past 5 years. It contains only 3 Damsels, and all fake corals for decoration, std strip light, and an undergravel filter. I use a power filter occasionally. The Damsels thrive, I have two Damsels that are approaching their 5th year. When I add new Damsels, and acclimate them as instructed, they adapt to the new water within a day.
Here's what's puzzling, and the point of my expermiment. I have not done a water change in 5 years. Replacement water for evaporation is all that I ever have added. My nitrates are sky high, immeasurable, and off the charts. My guess would be ppm in the high hundreds.
My simple questions is, how come I have no algae? Of any kind, and never have.