Instead of looking for leverage look for common ground, the ocean is so diverse that you can find any colour/pattern scheme that exist and one of the most amazing things about this hobby is how it can offshoot into so many others. Instead of twisting their arms and using their weaknesses play to their strengths!
My mom is all about one thing... Sparkles... Swarovski crystal dog collars, phone cases, glitter, precious gems ANYTHING SHINY. If she was the person I was trying to convince the glistening mantle of a maxima clam would be front and centre.
If your spouse is happiest when they are writing series of binary and algorithms let them do the code for your apex!
I'f they're into gardening then talk shop (SPS are full sun, softies are part shade) and let them help with your underwater gardening (they can even do it in winter).
If they're an artist have them help with the aquascape or the colour combinations in your zoa garden etc.
Knives and swords=sea urchins
stock
market= coral investments
Collectors=
WWC
Guns =Pistol shrimp
Boxing= Mantis shrimp
Adrenaline junkie=hand feed the snowflake eel
Wood worker= If only my tank had the most amazing stand in world;)
Anxiety= ultimate redundancy checker, they can see potential problems you'd never imagine! Plus blennies look like they're always mid panic attack
Chemist= test kits
Scifi/horror movies= bobbit worm
Astronomer: So they're saying one of Jupiters moons has ocean under all of its ice...
Hitting the club= turn up the blues on the LED!
Weight lifting= 1 gallon equals 8 pounds, let them bench your water change buckets!
Statistician: The probability of fish x and y's compatibility!
The list goes on and on.
Not only could this help get them interested but more importantly its a way they can contribute to something that makes you happy in a very meaningful way to the both of you. The only thing better than seeing someone you love be happy is being a part of why they're happy in the first place. They married you to involved in your life and your passions, if they're struggling to do that then help them find the connection and it will make it much easier!
The most important part: Get involved in their hobbies! Use the same connection tactics above and find a way to contribute to something that makes them happy. Even if neither of you ever get super interested in the others hobby at least you'll be spending time together and that should make you both happy:D