We have been maintaining two small saltwater aquariums for the last few months. Our main tank holds six gallons. Or secondary tank holds three gallons. Tanks of this size are referred to as nano aquariums because they are very much smaller than what was formerly considered a requirement for saltwater aquaria to succeed. Our experience, as well as many other in the hobby, has shown tanks can be viable at a much smaller size than the once-typical 100-200 gallon tank.

Our main tank has a couple fishes and various other living things. We've coined the term "diversity tank" because we basically have everything possible alive in it. One tunicate, which is doing quite well. A variety of worms spread across several animal phyla. Several soft corals, crabs, sponges, and a random bivalve or two. At least a dozen kinds of algae, mostly not green.

Oh yes, we also have two fish in the main tank. A Six-lined Wrasse and an Unarmed Perchlet (aka Red-blotched Perchlet, Geometric Hawkfish, Pygmy Hawkfish, etc.) Both fish are about two inches long.

The secondary tank was built to house a small crab which arrived in an order of amphipods/copepods/etc from a vendor in Florida. He's no longer quite so small and had to move out of the main tank because he was moving the rocks around and eating the hermit crabs when he could catch them.

Explanations and more to follow.