So congrats to you and I hope you really do get the chance to enjoy your money. You are 15, and starting a tank will likely provide you more value over the course of your life than investing 500 (enjoy the ecosystem and animals -> biology -> medical -> chemical engineering) (enjoy the great and technology, this is one of the greatest hobbies that has components of plumbing, electrical, and mechanical engineering).
But let me throw my 2 cents in here because I'm reading several things that are making me cringe (not the motorcycle comment, that was just funny). Some of the things were just flat wrong too.
First - if you want to invest, let's keep this really simple. I'll gladly debate anyone here about why my recommendation is better for him. You aren't 18, so you can't open a Roth IRA for yourself. However, you can open a custodial roth with with of your parents acting as the custodian. Ok, do your account is set up. Now because its a Roth IRA, you cannot deduct the investment on your taxes. You must pay taxes on your burger flipping. If you want more explanation about this - a conventional IRA allows you deduct up to a certain amount of investment into your IRA off of your taxes. The roth doesn't defer the tax, and you will go ahead and pay with a smile on your face.
You will keep your non 401K investments for retirement in a Roth IRA until likely your later 30s or 40s and stop investing in it. At that point, you will generally hit peak earnings for whatever career you go into. Maybe longer. But you now want to defer that tax and pay it all on the back end when you cash out the traditional IRA. Guess what - you paid hardly any taxes on this, especially on these initial investments while you were getting paid to flip burgers, work part time through college, get your first entry level "real job" etc etc. But the best thing is we are talking about potentially 30 years of growth with zero taxes on it once you take the money our and retire. And your taxes during that time were relatively low anwyays, Cool.
Ok So what to do? Get your parents to setup the custodial roth ira account and fund it with the $500. Vanguard is kind of the gold standard for IRAs and funds, but I think Fidelity and some others are catching up. The investment you are looking for - FOR ALL THE GLORY A YADA YADA - is a total market ETF (Exchange Traded Fund) with the absolute lowest expense ratio you can find. That's it. Anyone talking about mutual funds, doesn't understand. Anyone talking about a more balanced portfolio isn't giving advice to a 15 year old but to a 30 year old. Once you hit 30, start putting it into target retirement day ETFs and never have to worry about it again. These ETFs go "ok, so you retire in 25 years, you need a mix of stocks and bonds and that mix will change every year and we will completely handle that for you" That's it my man.
This is advice for retirement savings specifically because people today wait longer than ever to buy houses for a lot of reasons. I could write a book about this sections and how saving money today for a house downpayment you won't need for maybe 20 years (and maybe not even then) is not optimal.
As to the other and most important part - the tank. If you are $500 all in for a tank, pick up something like this with the light:
https://waterboxaquariums.com/products/cube?variant=31713752612973
Great little 10g tank that will get you 90% of the way to having what you need. Add a small 50W heater, some live sand, a little dry rock and an extra $25 for a hydor or other budget level pump. The final step here and probably the most important - get a few 5 gallon buckets. Buy a cheap RO Buddie unit that will give you 0 TDS water, and another $30 for salt mix. One of the 5 gallon buckets holds freshwater at all times and can be used for topping off and can quickly be mixed into saltwater if you ever need to do a major water change in case of emergency. The second is to mix salt water in, and the last one will be your old saltwater bucket that you can throw junk or bags, filter socks, old water, whatever.
Do a couple gallon water change each week on that tank and you keep just about any coral in it.
Good luck bud!
and get your self whatever you want!
