Small rudd are also very good pets, and are nearly as hardy and equally harmless.
Roach are easily obtained, and will not quarrel, but they are not quite so strong.
Perch, on the contrary, will live a long time if regularly fed, but it will not do to put any smaller fish, except sticklebacks, with them; yet they look so handsome that an aquarium containing two or three perch and a pair of sticklebacks is perhaps better worth looking at than one which can only boast of shoals of roach or other soft-mouthed fishes.
Dace and chub are pretty and harmless, but require more changes of water than is usually convenient, or they will soon die.
Tench are tenacious of life, but sluggish and fond of lying at the bottom. Small bream are fairly lively, and I have found them moderately hardy. They do not require water of special purity. Gudgeons live very well, and may be kept with minnows, being good friends together. The loach and the bullhead are fairly hardy, but have little other attraction. The grayling is very delicate, and it is not possible to keep her long, except under very favourable conditions. The ruffe or pope is hardy, like its relative the perch, and might, if obtainable (it is not a common fish), be placed in a perch tank, as a humble companion.
The bleak is almost as delicate as the grayling; and the jack is too ravenous for any fish to live in his company except another jack of his own size. This about ends the list, excepting that I’ve left till the last the noblest of fish—trout and salmon.
With regard to the latter I don’t want to encourage a boy in the notion that he can keep a ten-pound salmon in a tank.
Nevertheless, I have for many successive seasons kept salmon for weeks or months in a small tank; but these were young ones, very young, about the size of tadpoles, in fact, and not unlike them in some respects.
They are almost indistinguishable from the young trout with which I keep them. Of course, they are but babies, and they have their feeding bottles attached, and do not want feeding till these are absorbed.