A few days ago I went to Berlin aquarium with my sketchbook, I ended up staying in for 4 hours, one of which by the Arapaimas:
They are huge freshwater fish, growing up to 2m long (exceptionally 3 or 4) and weighing over 100kg. They moved around with little or no movements of their fins, like living submarines. Many people looked at them for a minute or two, fascinated by their size, but then walked away. I decided to stay and draw them, as they moved so slowly. I was therefore able to see them interact with each other and with other fish in the pool, and had a lot of fun when they flocked to observe people who sat next to their glass for longer than a minute – it was a very slow (5min? more?) alteration in their swimming patterns, from random to focused, so that in five or more passes near the person they finally stood with their head oriented to them, in a group of six and more. One guy leaning on the glass, busy on his phone, didn’t notice the slow formation of that fish crowd until other people pointed them to him, and he turned around to see the curious arapaimas then disperse with a powerful move of their caudal fins. One fish came to me to check my drawing kit, I showed it every piece closer to the glass, it observed everything and then swam slowly away.
I tried to draw and note as much as I could (in Italian – it goes faster for me!) and, as John Muir Laws suggests, to describe details, even if they seem obvious, and note questions. For example I observed the pattern of pink spots of several fishes and imagined if it could be a pattern that changes with age. I was not able to draw the texture of fins and head, so I described it in the notes. I liked spending that time immersed in observation. It felt a way of respecting these animals, even if they are living in unnatural conditions, hopefully pleasant for them anyway.