For those growing coral either as a hobbyist or a retailer, frag tanks is almost a must have as you propagate your coral to grow out in it. For the most part people tend to house their frag tank either at a side or behind the scene but still connected to the main water body of their display tank. The benefit of this is to maintain stable water perimeters as frag tanks tend to hold smaller water volume thus prone to status swings. By linking to the main system not only the water remain more or less stable. It’ll be a smooth transition too to transport the freshly propagated coral into the frag tank, or vise versa.
As for the dimension of the frag tank. I recommend something no less than 8″ deep but not more than 1′ high. This gives you enough room to maneuver also provide room for coral to grow if necessary, but not too deep to prevent light generation and water circulation issues. For the width and length, I guess it really is up to you on how much you wish to keep and how spacious if your set up.
One thing I need to point out is that many people ignored the proper movement in the frag tank. So I have seen many cases of “flow dead spot” in these type of tanks. One smart idea I have seen from a friend is to place buffers so the water flows through all corners of the tank.
