Most of us have seen the huge marine reef tanks with colorful fish and stunning corals. Saltwater tanks are, without a doubt, more costly, more effort, and more maintenance than freshwater aquariums. They are also worth all that you put in to them. You don't need a 100-gallon tank for a saltwater aquarium. You can successfully use a 25-gallon tank. The setup of a saltwater aquarium, however, particularly a smaller tank, does take some planning for success of the inhabitants, not to mention your sanity.
Before you begin getting equipment for your 25-gallon saltwater tank you first need to determine what variation of saltwater aquarium you would like. Mini-reef is just, as the name suggests, a smaller version of the big reef tanks with plenty of live rock, corals and smaller reef fish. If you're hoping to have a couple of the larger fish you can go with a fish-only tank or a combination of some live rock and some fish.
Some basic components of your saltwater tank will be saltwater, substrate, filtration, heater, lighting, and possibly live rock. This depends, again, on the type of aquarium you choose to set up. For maintenance, a good marine test kit as well as a hydrometer will be needed. These are the minimum components needed for a saltwater tank setup. Other equipment, such as protein skimmers, chillers and power heads can be added later should the tank seem to require them.
Saltwater -- Generally can purchase reverse osmosis (RO) water and marine salt to mix yourself or some good marine fish stores will sell "cured" water. This is saltwater that is biologically stable.
Substrate -- Crushed coral is commonly used, but live sand is becoming more popular and can help to stabilize your new aquarium. You'll need ½ inch to 1 inch of substrate.
Filtration -- A canister filter with areas for floss, carbon and biological substrate can help keep your water clean. Live rock crumbles can be used in the bio layer of your filter.
Heater -- Unless you keep your place a balmy 82 degrees F, you'll need a heater. Most fish and invertebrates need water 75 degrees F to 80 degrees F.
Lighting -- For smaller tanks the best choice, is fluorescent lighting. Normal output (NO) is more economical, but high output (HO) or very high output (VHO) is often needed for certain corals. The extra expense in lighting will be paid off in appearance as well.
- Live rock -- Live rock is the biological backbone of any reef tank. It helps to clean the water of ammonia and nitrites where are detrimental to fish and invertebrates alike.
A marine water test kit that tests for pH, ammonia and nitrates will be needed to ensure the environment of the tank is stable and survivable for your fish. Salinity, or specific gravity, is kept around 1.022 to 1.028. A hobbyist grade hydrometer (which measures specific gravity) is available at any saltwater aquarium store.
A 25-gallon tank will need chemical levels checked on a regular basis as the water quality can change rapidly. When selecting fish, a good rule is no more than one inch of fish per two gallons of water. Take into consideration when choosing fish what their size will be at maturity. A small tank is a bit more care and planning, but with a little effort you, too, can have the majesty of a saltwater tank.