Ways you can empty the pond fish and refilling it again
Catch the fish when the pool is almost empty. Although it seems stressful for them to be slithering around in the in the mud, it better than being chased around the pool by a lunatic with a net for half a day and still end up slithering around in the mud. Conscientious fish keepers will take this opportunity to check the health of their fish and treat any ailments accordingly. A tonic of a salt bath would help protect and repair them against the rigours of the upheaval. Cover and aerate the holding tank or containers. Dont feed the fish.
Continue to drain the pool and use the dustpan and brush with the buckets to scoop up the last few gallons of sludge keeping a beady eye open for small fish. Many wonders reveal themselves at this point; lost toys, money, tench that you may have put in 3 or 4 years ago and never saw again, also other fish of all sizes that you never knew you had. AND not forgetting the strange unearthly beings from the planet Zog.
Rinse down and brush off blanket weed growth. Don't use detergents but you can paint strands of blanket weed with an algicide if you want.
Check the liner. If you are looking for a leak, check the seams. Also as the liner begins to dry out, holes will become more apparent with water pushing back in through them from behind the liner.
Fill up
Start the refill as soon as possible, adding the required amount of de-chlorinator to the water. This may take 2 or 3 hours to do its job, so delay the fish transfer. Get on with replacing the plants as the water becomes deep enough to take them, which means lilies and oxygenators first. The marginals go in as the water level reaches the shelf.
All baskets in place and finishing the fill. Treat with pool conditioner.
For the fish, if there is a big temperature difference in the water in the holding tanks compared to the pool, transfer them in large plastic bags and float them on the surface with the sides rolled down to make a float until the temperature evens out. If you add little bit of the fresh water to the bag over a period of 15 to 30 minutes, this will speed up their acclimatisation to their new water. All this ritual and kafuffle is only necessary if you have particular concern for your fish. Im afraid to say, I generally just bung em straight in and let them take their chances its a tough world out there.
Once the fish have been removed from the old pool water, pour it back into the pool.
Only feed the fish very sparingly at first and dont think of adding any new fish at least until late spring next year.
Despite this being a small pond there was still a large amount of plant material to sort through and divide up for replanting. Here the old pruning saw came in useful again.
The Blagdon Water Gardens Pond after a complete restoration. It needed a complete rebuild since the liner had been peppered with holes by hungry herons. Because the pool liner went partly up the waterfalls, it meant the waterfalls had to be partially rebuilt as well.
Attacking the plants and replanting
Sometimes the big clear-out is not necessary but a pre-emptive strike on the water plants is required necessary for the coming season in order to keep the surface clear enough to still call it a pond. It may not be enough just to trim the excess growth emerging from the sides of the basket. The plants may be deserting the baskets completely in the search for more resources in the great beyond. You may also have become aware of an unwise decision in the choice of a particular plant and feel that before it causes a problem you may want to nip it in the bud, although the more apt analogy in this case may be to take the bull by the horns!
Get to grips with the clump. Ensure it will come away from its position so that it can be hoisted onto dry land for further attention. Here would be one advantage in having a concrete pond; you can be a little more blas about hacking lumps off without puncturing the liner. If it is too heavy to lift out it, it is probably best to get in there to pull the lump away from the side and attack the floating corpse.
Sometimes a clump will lift out partially and parts can be removed as it emerges. An old rough steel carving knife or an old tree-pruning saw are favorite. You will find groups of plants sitting in small planting baskets will no longer be separate and came out as one great lump, the plants having grown into each of its neighbours basket. The baskets may have to be abandoned.
One important note is that after all this activity of cutting back plants, removing and adding plant material and soil, check the filter and the pump regularly for the next few days. This plant sort-out and replant will result in a lot of extra material having to be processed by the filter. The disturbance to the fish will also create more stress, which will also indirectly put pressure on the filter too, so be prepared for a little extra filter and pump maintenance.