Overstocking a 20g long

[gilpi]

So you’re not actually overstocking, just having more guppies than is usually recommended. It’s not possible to literally overstock with livebearers, because they’ll adjust their numbers down to the maximum bioload for the tank.

This thread derailed so I'm staying away but couldn't help noticing that you have mentioned this in other topics as well. I have not heard of this.

 

[Ichthys]

This thread derailed so I'm staying away but couldn't help noticing that you have mentioned this in other topics as well. I have not heard of this.

There was a scientific paper written about this quite a few years ago. A series of identical tanks were set up (about 20), and each tank was stocked with different numbers of guppies, from 2 to 100. After a few months every tank contained the same number of guppies (somewhere near 50).
Livebearers will reproduce until the ‘ideal stocking level’ is reached, and then the bioload stabilises and remains constant. Fewer fry are born, less frequently, the fish stay smaller, older individuals die younger, etc, as somebody mentioned in that thread (apologies, can’t remember who it was).
In the tanks with few fish, they bred profusely and grew quickly up to the limit, as you would expect. In the overstocked tanks (above 50) fish died to bring the stocking level down to the ‘ideal’, and no or very few fry were born/survived until that ideal level was reached.