As long as you follow the rules that everyone else follows, I don't see any reason you can't post, as long as your parents are happy with it. My only thought is that as you are relatively new to ponding and learning fast, that you are cautious when giving advice. I'm sure you'll learn lots by being here, but there's no requirement to try and answer everything if you're not 100% sure on the answer. I will do some reading up just to make sure of the law here in the UK.
I also joined forums at a young age, and one of the things I remember is that I often tried to help when I wasn't experienced enough in the answer. Other members would get frustrated, as they must have thought I was an adult and didn't know I was much younger and trying my best - I soon learned it was good to ask questions and learn from others, then I was in a better position to help other people in time. You're going to learn lots about ponds very quick and you're in a place where lots of people will want to advise and help you where possible.
However, as you're on the web and we're treating you just like any other member, it does mean that I can't give you a free pass for things like advertising your own pond forum at the bottom of many of the posts you make (I've just gone through and edited them to remove it). I would normally bad someone for adding links promoting their own forum to the bottom of their posts. I know you're fairly new to the internet and forums though, so I'm sure you didn't intend this
.