I use google sheets. I log *everything.* I keep track of all of the test results, when I buy or service equipment, and when I get my CO2
tank refilled. I have separate sheets for plants and stock, and I track their acquisition date or birth, where I got them, where they are now, how much I paid for them, when they die and of what, when I sell or trade and to whom for how much. I have another sheet with all parameters preferences for each critter from several sources, each source cited.
I started out with an app, and I loved that I could attach pictures, but I couldn't change location. When I moved one snail to a different tank so I could treat an injury, all of its value was lost to me. I can't remember which app it was.
I spend a lot of time on this hobby.