The odds that the first thing the cat would try to jump on when it reaches stupid adolescence would be your tank are mathematically unlikely...particularly if you greet the first tentative try at the dining table with a water pistol.
Some tips on cat-training. 1. They're not primates, and don't respond to a spat or threat: they go into fight mode. They're not dogs and don't understand pack-leader. That's why a water pistol works well: there's no fight---it just arrives from Olympus. You should pet them if they desist from the behavior, even if your prize crystal is lying in pieces. they don't know about the crystal, but they do connect the praise with stopping, and will learn to pay attention to you, not run like a thief. 2. If you don't want the adult cat on the couch, don't put the kitten up onto your lap. 3. If you don't want the adult cat to be curious about the fish, don't show them to the kitten. 4. and they can learn to discriminate among forbidden things---my cats will break their necks to avoid stepping on a paper [I write], know that the couch is fine but the dining table and kitchen counters are verboten [I still have to reinforce that one now and again] and generally know the command 'claws!' which means the minute claws come out in play, you tap the offending paw gently and make the claws retract, gently. They know words, and "no tooth" [stop all fun and tap gently on the nose] and "claws!" are two to teach early and consistently. Do not allow them to claw you while their claws are tiny; ditto biting and teething. [I take it this is a first cat.] Miss Cuisinart, as we call Ysabel, comes from a breed raised to protect temples, so the saying goes, and I'm very glad to have taught those two commands early. They will not learn it later.