Less than 100 Liters is very difficult to manage but aim for 500-800 Liters at very minimum because you will want to make your pond bigger later. This can fit in any a little boring coin of a garden and will became the best part of the garden. Everything in a range of four to ten liters is not a pond, is a dog bowl and will became a mosquito nursery. I see those often adviced by youtubers that never tried to manage a pond seriously.
Beware. Ponds of all sizes are dangerous for toddlers and ponds must have a side with a gently slope so falling pets and animals can climb out. If you have children of less than five years, you --must-- cover the pond with a solid iron pond cover:
Beware. Ponds of all sizes are dangerous for toddlers and ponds must have a side with a gently slope so falling pets and animals can climb out. If you have children of less than five years, you --must-- cover the pond with a solid iron pond cover:
https://duckduckgo.com/?q=pond+cover&t=newext&atb=v411-1&iax...
Apart of this the "deeper" the pond the more animals will fit for the same price. More than 1 meter is normally unnecessary in a small garden