It's time to step away from auto and play in manual... ;-)
At first your results will suck. You'll hate your camera and possibly even yourself. But stick with it and you'll find that it's really not that hard and your results will improve.
I don't recommend starting down the manual path with the aquarium though. Find something dry that you can play with, something where you have full control of the camera and subject.
Start out in either Aperture priority (Av on the mode dial) mode or Shutter priority so that you can get a feel for what your changes do and still get assistance from your camera. In case you aren't aware, Aperture priority, you control the f stop. The camera will figure out the shutter. You can get a better feel for depth of field and how your adjustments affect it. You can also get a better feel for how your flash works with those settings. When I was shooting racing, I always shot in Av. I didn't have time to figure out Shutter speed. I got pretty good at finding an f stop I wanted for a particular shot and let the camera work out the rest.
Then try out Shutter priority (Tv). This is the inverse of Av. You control the shutter speed, the camera figures out the f stop. Shooting racing, if I was looking for a good motion blur shot, I'd switch to TV. (I had it already setup so I could switch the mode over and it'd be setup how I liked it.
Once you get a feel for those modes and how they affect the results, try going manual.
If you're like me and are furloughed and have time, it's worth the experimenting.
Before I got over my fear of M, most of my shots were ok at best. With film it was a much more difficult decision to take control due to the cost of film and processing just to find you didn't have a clue. Digital removes that cost completely. And, if you can connect your camera to a laptop, you can see on screen immediately the results and master manual in no time.
You definitely don't lack talent, just practice.
