CHAPTER VII.
GENERAL MANAGEMENT.
I shall in this Chapter only notice such particulars in the management of aquaria as belong especially to the marine department, since some of the directions given in the former division of the work apply to tanks of all kinds, and need not be repeated. When preliminary difficulties have been surmounted, the matter of first importance is the selection of the stock, and its arrangement in accordance with just principles.
Grouping.—In Chapters IV. and V. I have enumerated the kinds of animals and plants most suitable for aquaria, and must now caution the beginner against the injudicious grouping together of creatures of dissimilar habits. Anemones may, as a rule, be kept together. The several species agree well, and seldom or rarely injure each other; but star-fishes and crabs are best kept in vessels apart from them. Star-fishes are very destructive, and readily absorb the bodies of mollusks out of their shells. If exception is to be taken to any particular anemone, I think the grand plumosa must suffer by it; for this noble creature gives off a flocculent exudation, which seems injurious to other kinds. I have generally kept the plumose anemone in company with A. mesembryanthemum, A. bellis, troglodytes, and others, without perceiving any bad result; but I have always been careful to remove the slimy exuvia daily, by means of the dipping tube. Respecting mollusks, and especially trochus and
