Well, no, your tank doesn't need either, considering its rather small volume of water. Most, if not all of the excess nutrients can be removed just by performing your weekly water changes. That will also help to replenish the elements your saltwater aquarium needs to survive, such as iron, strontium, calcium, etc..
BUT, personally I do recommend converting a HOB
filter into a tiny refugium because it will make all the difference. Should you slack up on your water changes a bit, the chaeto, provided it has enough light to grow, will do a great job of filtering out excess nutrients.
As for supplies, you should consider the Aquaclear 70 filter. It's pretty big, but still small enough to fit on your tank. It will also provide a decent amount of flow. Also, if you choose to, you can remove the heater from your display tank, and buy a Hydor Theo 50w heater. It provides plenty of heat and it is small enough to fit in the HOB
filter without any problems. This is the setup that most people are putting on their nano tanks.
Have a read at this website. It lists exactly what you need, and how to setup your own little HOB
refugium for a very little amount of money. http://www.nano-reef.com/forums/inde...&#entry2004830