Width: You should get the widest tank you have available considering the space you have to allocate for it. A mistake would be thinking that upgrading to a wider tank later would be easy. You might be able to get a larger tank but you would also have to upgrade all of the equipment in it, making the upgrade project up to five more times as expensive then if you get the largest tank that will fit in the space you have allocated as possible. Also in that regard, fish tend to grow when you feed them. If you get a small tank and your fish grow, you will have to upgrade to accommodate them. But if you start with a wide tank from the start, then when your fish grow you will only have to provide them will more food. The environment you first created will still be sound.

Height: Fish swim horizontally not vertically, so the more feet wide your tank is, the happier an environment you are creating for your fish. A mistake is to think that height matters. Unless you are getting very big fish, then a higher tank will only make it harder to provide the right lighting. Opting for a wide, low tank is a much better option. Your fish won't know the difference, but you will when you get your water and electricity bill.

Water: No matter what size you select for your saltwater tank, you will want to have access to water for the purpose of making the task of changing the water in your task easier. The last thing you want to have to do is cart fifty-five to a hundred gallons of water up or down a flight of stairs. If you can be assured that you can at least have a hose to move your replacement saltwater into your tank, then you will have a far easier time changing the water, which you will want to do because of the positive effects on your livestock and the negative effects that changing the water has on pesky algae.

Environmental Factors: You want to keep your tank away from anything that will affect your ability to control the environmental factors in your tank. Allowing sunlight to beam onto your tank is a mistake as it will cause both heat and light, and will encourage algae to grow, and saltwater plants to not grow as well. Next you have to look at radiators or heaters, and ensure that your tank is not near them because the heat generated will definitely cause your control over the environment in your tank to get out of your control.

Type: Initially, acrylic may appear to have a nicer image, but it is very easy to scratch, and over time, micro-scratches create a dull look that counter-acts the initial beauty. Regular glass tends to look a bit greenish because of the iron, so for the best look, spend the money and get a tank made of low iron float glass.