Three stages to this; and I'm only halfway through the 1st. Sigh

1) Hardware, I have a design, and a (good) pcb plot now. I want to prototype the speaker/buzzer driver circuit before I finalise and make the PCB. It's still a bit of (educated) guesswork design.

2) Then I need a software framework.

3) Finally the fitting into an aquarium; which is not a trivial task.