This is a common question for new reefers and something that is essential to know to keep a successful reef system. This is what I use to set the parameters in my tank, but others may recommend something else.

Nitrite and Nitrates should be as close to 0 as possible. Nitrites are not as much a threat to reef inhabitants as Nitrates. Once your nitrate levels reach the 20 ppm level, it is time for a water change. Nitrates are also associated with algae growth and can cause sickness in fish, inverts, and corals

Another way to control your Nitrate levels would be with the use of a refugium where you can grow macro algae and having a deep sand bed. Also, over feeding can raise your nitrate levels

pH can also cause sickness with the specimens in your tank. This can be controlled with the use of balance blocks which you can find at your local fish store.

Salinity. There are many ways to measure salinity including conductivity probes, refractometers, and hydrometers. Salinity is very important in the fact that if your water is too salty, it can burn your fish and kill many sensitive corals. You will want to stay right around the 1.026 area, but less is better than more

I use a simple hydrometer that works perfectly

Ammonia is released by all animals and some other things that live in the reef aquarium. Unfortunately it is a very toxic chemical that can have dire effects on your reef community. Macro algae is a good way of controlling your ammonia levels. Ammonia is also used by bacteria in the creation of Nitrites and Nitrates which are also toxic to your reef inhabitants.

Temperature can have various effects on your system. At higher temperatures, your fish metabolic rates increase causing them to use more essential nutrients and excrete more toxic ones. inversely, a lower temperature will slow metabolic rates and allow for more oxygen retention in the aquarium. However, most corals live in waters in the 80-86 degree range, so it is optimal to keep temperatures somewhere between the 79-83 degree range.

Calcium is a very important chemical for reef systems simply because it is what corals use to form their “skeletons.” Studies have reported than having your calcium levels above the recommended levels will not help your corals grow any faster. If your system is in need of calcium to be within the recommended level is to add calcium chloride.

Alkalinity is used with calcium to make coral backbones. It is imperative for people trying to grow corals to maintain alkalinity and calcium levels for optimum growth. If you need to supplement more alkaline, you can simply add baking soda or washing soda (I have only read of this, never implemented).

Phosphates are normally introduced to your system through the food you feed your animals. Phosphates can also cause algae growth to become a problem in your tank and is one of the reasons it is highly recommended not to over feed your fish. Growing macro algae is a good way to control phosphate levels as well as skimming.

Magnesium is another chemical that is used right along with calcium to create coral structure. the natural level in seawater is 1285 ppm and it would be best to stay around that level.