Here are some gift suggestion for that marine aquarium hobbyist( or someone who wants to become a saltwater aquarium hobbyist) on your gift list.
From providing the bubble to protein skimmers to circulating water in the tank, to providing oxygen to the tank occupants, air pumps serve many purposes in saltwater aquariums. Most air pumps wear out on a regular basis. Diaphragm air pumps are notorious for loosing air pressure over time. You will be a big hit if the aquarist on your gift list receives a quiet, powerful, long lasting piston driven air pump if they utilize an air pump in their aquarium system.
The internet is great for doing research, but nothing really beats sitting down with a good book. Books about aquarium setup, corals, fish and invertebrates always dominate a good bookcase. Every aquarist appreciates the information and fantastic photos in a good aquarium book.
Maintaining a stable water temperature is essential to the health and well being of the fish, corals and other invertebrates in saltwater aquariums. Every aquarium needs to have its temperature accurately monitored to maintain its stability. While chasing a floating or sinking thermometer around a tank might be fine for some, most aquarists really appreciate having a state-of-the-art digital thermometer with a probe. Some of these thermometers are wireless and can even monitor up to 4 tanks at the same time.
Automatic fish feeders are not only useful when you are away from home for a few days. Many aquarists use automatic fish feeders on a daily basis to make sure that their tank occupants are consistently fed a measured amount of food on a regular basis. Look for the feeders that dispense flakes and granules as well as keep the food dry.
Nearly all saltwater aquariums (particularly reef tanks with corals) utilize at least one powerhead for water circulation. Magnetically attached articulated powerheads have recently hit the market with great success. These powerheads are adaptable to almost any aquarium water circulation requirement. A great gift for any aquarist.
Over time, almost every saltwater aquarium will experience at least one outbreak of red slime algae (cyanobacteria) at one time or another. You will definitely be remembered when your favorite saltwater aquarist finds that he has a Red Slime cure at hand when he/she has their first outbreak. Not really all that expensive, but a "must have on-hand" for every marine aquarium.
Test kits are something that every saltwater aquarist uses on a regular basis to keep track of their water parameters. Because of their convenience and accuracy, the dip strips are particularly popular. The dip strips which include tests for nitrites, nitrates, pH, hardness and alkalinity at one time are particularly useful and popular.