The tank, having been prepared and seasoned with the same precaution used for the river aquarium, and having a clear bottom and a supply of good water, is now ready for planting. Many beautifully colored and delicately fringed Algae and Sea-Wracks will be found on the rocks at low tide, and will sadly tempt the enthusiast to consign their delicate hues to the aquarium. All such temptations must be resisted. Green is the only color well adapted for healthy and oxygenating growth in the new tank. A small selection of the purple or red varieties may perhaps be introduced and successfully cultivated at a later day, but they are very delicate; while the olives and browns are pretty sure to die and corrupt the water. It must be remembered, too, that the Algae are cryptogamous, and bear no visible flowers to delight the eye or fancy. Of all marine plants, the _Ulva latissima_, or Sea-Lettuce, is first and best. It has broad, light-green fronds, and is hardy and a rapid grower, and hence a good giver of oxygen. Next to this in looks and usefulness comes the _Enteromorpha compressa_, a delicate, grass-like Alga. After a while the _Chondrus crispus_, or common Carrageen Moss, may be chosen and added. These ought to be enough for some months, as it is not safe to add too many at once. Then the green weeds _Codium tomentosum_ and _Cladophora_ may be tried; and, still later, the beautiful _Bryopsis plumosa_. But it is much better to be content with a few Ulvae, and others of that class, to begin with; for a half dozen of these will support quite a variety of animal life. After a few hardy plants are well set, and thriving for a week or two, and the water is clear and bubbly with oxygen, it will be time to look about for the live stock of the marine aquarium. Fishes, though most attractive, must be put in last; for as they are of the highest vitality, so they require the most oxygen and food, and hence should not be trusted until everything in the tank is well a-going.