Here is a list of some great resources that pertain to the

Calculators

Reef Chemistry Calculator – JDieck – Ca, Alk, Mg, affects of additive brands etc.-

Calcium Reactor Calculator -- JDieck -- How to dial in a Calcium Reactor

Water Volume Calculator -- JDieck -- Type in your dimensions and see an approximate total water volume

Water Change Calculator -- Hamzasreef -- Type in your dimensions and see an approximate total water volume

Coral & Fish ID

Fishbase -- Database of information on Marine Fish

Algaebase -- Database of information on algae

Reef Forums

Humble Fish -- Need help? Have a fish disease question?

Reef Central -- Another forum with great information. One of the original Marine Aquarium hobby forums

Reef2Reef - Another popular forum