I agree with Scott and Brian (who, BTW, have both been very helpful to me). My pico was my first SW tank, but before I started it up I had done a lot of research online, and I'd worked for a LFS and gotten a bit of SW experience that way. I also have a few years of FW experience so that helps for sure with knowing how to do maintenance and what not.
That's a cool tank and I believe it's worth $25, but bear in mind that a pico tank is pretty much the most difficult route you can take into saltwater aquaria. I'm not trying to discourage you at all, and I do believe that if you do your research and ask questions here that you can be successful with it. But it is going to require daily attention. You'll need to top it off every day with FW so the salinity is stable. You'll need to do pwc's at least once a week, and you'll have to have SW on hand already mixed up for this purpose. Also, understand that there are more things that you will need to buy than just what comes with the tank, and you will end up spending more than what you probably expect. You'll need a powerhead to mix and aerate your SW. You'll need a hydrometer at the very least, but they are so inaccurate that I just threw mine in the garage and bought a refractometer (a lot more expensive, but totally worth the money). You'll also have to buy salt mix- this won't be a huge cost for you since a bag of salt will last a while, but it will be an ongoing cost. Plus, it is recommended that you use RO or RO/DI water to mix up your SW instead of tap water, so you'll end up buying water too.
You can set up a pico tank that will be cheap relative to larger tanks, but compared to FW it is still very expensive. I've spent nearly $300 on my tank and the stuff in it, and I already had my rock and filter.
Again, I'm not trying to be discouraging at all, I just want to make sure that you know what you are getting into. I had a pretty good idea of what I was getting into, and the cost still has managed to surprise me! Good luck.
