To start a tank you need to know what kind of fish you are planning to have, either aggressive, community fish, etc. That is the main thing you need to know so you can find out what the right size tank is good for you. Also you will need to know what space you have available in your house or office. Once you find that out you now have the decision of either getting an acrylic or glass tank. The good thing about acrylic is that they are light weight and have round edges. A bad thing about acrylic is that a piece of coral or something can scratch the tank pretty badly, then you have drain all the water out and fix it, but if the scratch is on the outside you can fix it easily. Now for the glass tanks they are a bit heavier and doesn't scratch as easily, but is also a good choice. Also you need to decide if you are planning to have reef tank or just fish tank because the lighting and filtration requirements are very different for both.

    If you want to have a marine tank for the least amount of money then go for just a fish only tank because many corals out there are very expensive and require expensive, intense lighting and filtration. Also the maintenance between fish and inverts is tremendous. The inverts require the right water quality and you have to add chemicals each week/day etc. If you decide fish then you need to know what kind of fish because some fish are only to be kept with themselves such as seahorses. They are only to be in a single tank by themselves because other fish will bother it or eat all of the food before the other fish has a chance. But if you want to have a community fish tank then there are many choices of fish out there that you can get which will go along with each other. Some fish are very very sensitive like butterflyfish and should only have the best quality water. The last choice is to have a fish and invert tank. The price for one of these tanks depends on the inverts you get or the fish that you get, and the maintenance is between an invert tank and a just fish tank. For this type of tank you should only get a few fish because inverts and corals are a lot more sensitive to fish waste.