What is the required salinity of a salt water aquarium?

Answer 1

http://reefkeeping.com/issues/2004-06/rhf/index.php

shows a salinity table.

Answer 2

This depends on whether you're keeping invertebrates in the tank or not. Natural seawater has a salinity of 1.024-1.026. Inverts need this level. If you're keeping a fish-only tank, it keeps them a little healthier (reduces parasites) to lower the salinity a little to 1.020 - 1.023.

The reasoning is the same as for adding aquarium salt to freshwater fish - all fish need some salt, but freshwater provides too little, saltwater provides too much! Fish expend energy to acquire/expel salt, so changing the salinity in the necessary direction allows them to use that energy for other functions (growth, reproduction, disease resistance). Parasites & disease organisms not adapted to the higher/lower salinities don't fare as well!

Answer 3

Salinity, measured as specific gravity, can be kept low in a fish only aquarium. Typical specific gravity for the water in such a tank would be 1.018-1.022. Lower specific gravity helps to prevent parasites. Nitrates should be kept at 80 ppm or lower; 30% water changes may need to be done as often as once per week to maintain such a nitrate level.

8.0-8.4 PH Depending on your fish / cridders

Ph and salt requirements depend on what you have in your tank. Some require a bit higher some a bit lower most somewhere inbetween.

The invertebrate only aquarium is probably the most practical saltwater set-up for a small tank (20 gallons or less), and can often be done without any special lighting. It would typically contain starfish, urchins, shrimps, lobsters, crabs, cucumbers and tube worms. It would be set up similar to a fish only aquarium, but would almost certainly contain live rock, as it should never have to be treated for parasites and many creatures in the tank will feed off of it. Substrate is not required, but would be recommended as some invertebrates like to burrow and dig. A protein skimmer could be helpful in this aquarium, but may not be necessary if the tank is not heavily stocked or overfed. A specific gravity of 1.023-1.025, a temperature of 74-78º F, and a nitrate level of less than 40ppm is essential. Water changes of 30% may have to be done every 2-3 weeks to maintain such a nitrate level, and trace elements such as iodine and calcium may have to be added intermittently. If anemones are to be kept one watt per gallon of lighting, including some actinic (blue) light, is a must, and nitrate should be kept as low as possible. Certain anemones may need more light; others do not need any.