MAKING OUR HOME BEAUTIFUL 225
amount of food need be left to decay. If, for any reason, the food is not all consumed, or if there is any accumulation of other matter, it may be readily removed by means of a long pipette, or a rubber tube used as a siphon. For the small aquarium a pipette with an inside diameter of one-quarter to three-eighths of an inch, and fitted with a large rubber bulb, is most convenient. In using the tube without the bulb, place the thumb over the upper end of the tube while introducing it, then withdraw the thumb when the tube is immediately over the substance to be removed. The substance will rush up the tube, after which the thumb is replaced while the tube is withdrawn.
For larger aquaria the pipette is rather tedious and the siphon is recommended. In either case the waste should be strained through a cloth net and the water should be returned to the tank rather than add fresh water to replace it.
The less changing of the water the better, for fear of introducing some new factor to interfere with the adjustment already established. It will occasionally be necessary to add water to replace that which escapes by evaporation. This should be done a little at a time and care should be taken to have the temperature the same as that of the water in the tank.
For the purpose of removing any deposits on the glass of the aquarium, a swab can be made out of a stick with a bit of cheesecloth wrapped about the end. The cloth may be removed each time it is used, which should not be more often than is necessary to keep the glass reasonably clean, or if it is used again it should be carefully cleaned and sterilized each time in hot water. The swab will serve not only to remove ordinary dirt, but also the green scum of the minute plant life which in strong light will soon cover the glass. These minute plants do no harm—in fact they are as beneficial in yielding oxygen as are the larger ones—and they are a natural part of the balanced life of the aquarium. However, one keeps an aquarium to enjoy the view of its miniature water world, and if the green scum interferes with the view it may be removed without great detriment to the adjustment. The scum grows