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An Ecosystem's Equilibrium, Balance, Symbiosis
The Christmas Day Bird came back last night. Probably a regular "late hour" visitor. Time will tell.
The birds are doing OK and this Christmas was relatively warm and not wet, which is likely good for the birds. It's convenient for humans, too.
It'll soon be 12 months since we last changed the whole (not small, partial replacement) water in the fish tank to clean all the objects in it, including the gravel (or rocks). We have several sets of objects so that the fish tank can look different each year (or throughout the year).
12 months would be an all-time record. Typically there comes a time - or a season - where some green growth overtakes the other organisms and they cannot consume it faster than it grows. Even adding all the solutions and potions might not help.
This time one thing is unique: shells. There are 3 or 4 of them inside the fish tank.
The shells are reproducing in the fish tank. One was 'accidentally' entered along with the loaches from the shop. It has since then made offspring and they're growing quite big, though they help the loaches clean the rocks at the bottom and sometimes the glasses on the sides.
In hindsight, adding some shells to a fish tank is probably a great idea. They're like an underwater janitor. █