Good on you for wanting to work for your hobby! A good work ethic at a young age will get you very far.
One thing I don't think has been covered yet though that you will have to learn as you get older (and I don't mean to be a downer, just some friendly advice) is to live within your means. Learn to budget well, and don't over do your budget (as it seems you have done since you said you were having trouble keeping up financially with your hobby). Work out what you can afford per month, and stick to it.
Not only will it help you with your fish hobby but its also a great life skill. Good luck finding work!