After going to the expense of buying a pool some people are inclined to throw in one or two plants, a couple of goldfish and then leave them to fend for themselves. After a year or two the fish may be dead and the plants a tangled unsightly mess, whereas with just a little attention for a few days in the spring and the autumn the pool can be turned into the focal point of interest for the whole garden.
Whether your pool is neglected, or not, Spring is the time to give it a clean. Carefully catch any fish and place them in clean buckets, or bowls (NOT GALVANISED) remembering that the water absorbs oxygen through the surface of the water, so a deep receptacle will not hold any more fish than a shallow one.
You may also like to save a little frogspawn if any visiting frogs have obliged, as it can be a useful addition to the pool. The frogs spawn itself is good fish food and any tadpoles that hatch will provide valuable nutrition for the larger fish as they start feeding in the warmer waters of the spring. The tadpoles also clean the pool eating any dead vegetation and decaying fish food. Next remove all the pots of plants and keep them out of the sun while the water is siphoned, bucketed, or pumped out.
There is no point in scrubbing the pool spotlessly clean because in a few weeks it will be green again anyway, but do remove all the foul smelling sludge before refilling with tap water. The tap water will contain chlorine and may contain fluorine that can harm the delicate membranes in the fish’s gills.
This problem can be removed by adding a chemical that is designed to neutralize all halogens and is widely available from aquatic retailers. Alternatively the pool can be filled and the water left to stand for a few weeks before adding the fish. However, in practice if plants are added to the pool, the fish can be introduced straight away with no real harm, as the chemicals and organisms in the pots of plants will naturalize the water.