I'm sorry your parents are so clueless about the fish.
Being interested in, and fascinated by fish is not weird. Really. (Of course, here I am on the fish forum, so you know I'm not exactly unbiased). Look at the stuff supposedly "normal" people are interested in.... Fashion? Pu-leeze. I mean, either you look good, or you don't. One day, flats and bell-bottoms are in, the next, 5-inch platform heels and hip-huggers. I wear what I like, what is comfortable and fits my body shape, in the colors I like, and don't give two whoops about what everybody else is wearing... except sometimes to express astonishment at how impractical some garment is.
What the "hottest" Hollywood star is doing or saying... the latest trend in "must-have" widgets... watching grown men paid to chase around balls... why should an interest those things be considered "normal" and fish-keeping not?