Wooden fish pond to raised bed

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melliff
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In my new property, I have inherited a wooden walled fish pond. I don't want to keep fish and it would make a perfect raised bed for a herb garden.

It measures 6 feet by 4 feet and is 3 feet deep. I assumed that it was just lined with a rubber membrane but when I emptied the water and removed the bottom of the lining I discovered that it has a concrete floor. I hammered a bolster into it and it appears that the concrete is over 6 inches thick.

I had thought to break up the concrete floor or at least puncture it with holes for drainage but I won't be able to do it with my tools.

Before I employ a man with a jack hammer, my question is this: if I fill the bed with 18 inches of rubble and then with about 18 inches of soil and compost, will it matter that the bottom is sealed?
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Diane
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I'm no expert - but it will probably be ok for a bog garden. Monty Don plants his hostas in his bog garden area. And it might get a bit smelly.
'Preserve wildlife - pickle a rat'
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oldherbaceous
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Afternoon melliff, as long as the the boards aren't water tight at the bottom of the wooden sides and ends, your suggestion of half hardcore half soil will be excellent for herbs. If it looks as if it might hold water, you could drills holes low down in the wood to allow for drainage. And if you think you would like veg, i would put less hardcore and more soil.
Kind Regards, Old Herbaceous.

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sally wright
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Dear Melife,
I would find someone to drill or core out some holes into the concrete, you won't need many.
Put a layer of weed fabric over the holes and fill the base with about six inches of gravel or dust free hardcore.
Apply a second double layer of weed fabric so that you can staple it to the sides about six inches up from the gravel layer; but do remember to leave a bit of slack in the fabric to allow for settlement.
Then as a final thing use the remnants of the pool liner to line the sides of the planter with an overlap of the weed fabric.
Using the pool liner in this way will keep you from damaging the timbers when you are cultivating the soil in the planter.
It is good if you can keep the soil away from the wood as you never know what the timber has been preserved with and it will help to make the timber last longer.
Also drilling holes through the woodwork will expose the interior of the timbers to rot as many preservatives are only in the outer layers of the wood.
Fill with a soil mix of your choice although I think ericaceous plants would be a good choice such as blueberries and cranberries.
Regards Sally Wright.
Monika
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You don't say where you live, Melliff, but if it is an area of high rainfall, I wonder if you could be in trouble just when everything is growing. Would it not be possible just to drill a few holes into the concrete with an electric drill and a large bit? Then cover these up with curved shards before you put in some rubble?
melliff
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Thanks for your replies. The concensus seems to be that it will need drainage which was my own thought. I shall buy a very long and thick concrete drill bit and hope that it breaks through the concrete. The previous owners must have kept Great White Sharks in the pond to need such a strong bottom.
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Diane
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I don't suppose any of the previous owners has been reported missing in mysterious circumstances :roll:
'Preserve wildlife - pickle a rat'
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