Ordinary builders’ sand should not be used simply because it’s challenging to clean and packs tightly, making it tough for plant roots to penetrate, and it doesn’t permit the water to circulate. The very best sand could be bought washed ready for use. Nevertheless, it should be washed again just prior to you put it into your aquarium, as it’s certain to have collected a quantity of dust whilst in store. This sand is truly fine grit of a pebbly texture, ranging in size from about & in. to J in. It should not be larger as bits of uneaten food may fall between and cause the water to foul. It’s also worth noting that any large stones put into the tank for decorative effect should be pressed well into the sand for the same reason.
The depth of sand could be varied to suit your individual taste, but for general purposes I have found a 2-in. layer of sand ideal.
The sand should be thoroughly washed with successive rinses of water, and stirred until the water remains clear when the sand is disturbed. It should then be boiled in a bucket to ensure that no germs are introduced into the tank, and washed again. This may seem a trifle fastidious, but it means that when the tank is finally set up, your aquarium will be in a healthy state and, if you take reasonable care when you introduce new plants and fish, it will remain healthy. Do not be tempted to put a layer of earth under the sand in the misaken idea that it will assist the plants to grow. It doesn’t work out in practice.
Remember the fish provide nourishment needed by the plants, but if the temptation is too great to overcome, and you feel you must experiment, use potting compost or clay, or try a mixture of one third peat, one third clay and one third coarse sand-this planting medium has the advantage of being proven, to some extent, by Dutch aquarists. Nevertheless, if you are experiencing your early days of fish-keeping, start with sand, it’s much safer, and remember; under no circumstances use garden soil.
Attractive presentations and lay-outs could be effected by sloping the sand from about 4 in. at the back of the aquarium to about 1.5 in. at the front, or any other gradient that is pleasing and practical. Such an arrangement shows the plants to better advantage, and encourages the sediment to drift to the lower level, at the front of the tank, where it could be easily siphoned off.
There is a minor problem in retaining the sandy slope if it’s steep, simply because of the natural tendency of sand is to flatten out when saturated with water. This could be overcome by pressing strips of thin Perspex vertically into the sand to form barriers, and concealing them with a further layer of sand. When you are planting or doing any other work in your aquarium which disturbs the base and makes the water cloudy, you will discover when it settles that it leaves a thin dirty film over the top of the sand. Siphon this off.