You can tell your parents about the educational/scientific/research benefits of fish keeping. This is what sets keeping fish apart from having a pet dog or cat. To successfully raise fish, you have to know biology, chemistry, ecology, environmental science, psychology, and much more. There's also some engineering involved if you want to DIY your own tank/pond.As some of you already know, i have 4 irredescent sharks(1 12inch, other two 7 inch and the last one 6 inch),four silver dollars, one oscar, one zebra tilapia and one raphael catfish in a 120 gallon four feet by four feet pond. I already know they don't have enough space and i have trying to convince my parents to buy me a bigger pond. We don't have much money, so they told me to sell my two parrots(out of 22) to get some money and buy a bigger pond. I tried to sell them but failed. I expressed my problem to my parents but they ignored and said"they have enough space and we don't care if they die or not". This saddened me and so i have decided to give away all my collection for free. At first i hesitated because i knew that no one who lived near me had a big enough space for them. But i have no choice since i can't watch my fishes die in my own hands. When i was first buying them, my elder brother and parents assured me that they would buy me a bigger pool a few months later but they didn't. Just wanted to share my story.
Just from my own story, keeping fish was actually the factor that motivated me to pursue biology/pre-med in college. In high school, I did a research project on my cichlid's aggression and presented it at many high school research competitions. In fact, I even wrote about keeping fish in my college essay and how it made me interested in research and bio/pre-med. Through this, I was able to get into Johns Hopkins and now that I look back, I realized that I wouldn't have been able to do all this without buying my first every fish tank in 7th grade.