Hoping to Convert an old concrete chlorine pool to natural pool/pond

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Hi
I’m hoping to get feedback and advice on the ideas i have.

I’m looking to take an old pool (18x36’) and convert it to a natural pool with water plants, some frogs and small fish. Maybe a couple of turtles. Also looking for the water to be clean enough to swim in. I dislike chlorine pools. I love natural places to swim.

So far I’m looking at a three-pronged approach to filtration:

1) Gravel bed filter-
Creation of a gravel- bed system on the floor of the pool (in the shallow end). Includes a layer of shallow milk crates on the floor of the pool to create a void space; a layer of landscape fabric over the milk crates, a layer of gravel (18”?) over the fabric. A pvc pipe running on the pool’s floor from the milk crate void to the pump. Some lily pads or lotus growing in the gravel?

2) Bio-filter barrels and waterfall/fountains- Construct a large framed box (podium-shaped) to hide bio filter barrels, pipes and pump. Also to create attractive design and elevation for waterfall and maybe fountainheads. Build apx 36”Wx24”Dx6’H framed box (2x4’s & plywood?) at the head of deep end. Two 55gal drums as bio filters joined in circuit use of diy bio balls within. Input pipe from shallow end gravel filter and one additional pipe from bottom of deep end. Use of ball valves to control flow into and out of pump to/from each point.

3) Raised bed channels-
Rather than reduce space within the pool for filtration why not use the perimeter of the pool? And gravity for more waterfalls? From the tall podium style box mentioned above, build two L shaped “raised bed” style (18”Hx24”W?) boxes/channels that run along the sides of the pool. Build strong and line the inside- then fill with gravel. A fountainhead on each side of the taller podium box will be the input to each channel that then runs apx 6’ along the head, then apx 10-15’ down each length of the pool. A waterfall at each terminus would spill back into the pool. Water Plants can be grown in these “raised beds.” Decorative and edible.

The good thing regarding the above is that I can start with 1st idea and see how things develop before I create the 2nd and wait on the 3rd. It seems flexible to me at least.

What do you all think?
Hoping for Feedback and Ideas!
 
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I decided to add these (bad) drawings to help make sense of my ideas.
 

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Welcome to the GPF.

I'd suggest you search YouTube for ideas - I've seen a number of people do these conversions.

Here's one:

 
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Welcome to the GPF.

I'd suggest you search YouTube for ideas - I've seen a number of people do these conversions.

Here's one:

I have been looking at many of these videos. While I have learned a lot from many, I’m still hoping for direct feedback and insights from people and their experiences. And to start a conversation.
 
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1) Gravel bed filter-
Creation of a gravel- bed system on the floor of the pool (in the shallow end). Includes a layer of shallow milk crates on the floor of the pool to create a void space; a layer of landscape fabric over the milk crates, a layer of gravel (18”?) over the fabric. A pvc pipe running on the pool’s floor from the milk crate void to the pump. Some lily pads or lotus growing in the gravel?
DO NOT PLACE FABRIC OVER THE MATRIX BLOCK start with larger rocks that won't fall through, then step down to the next size and finishing with 3/4vor 3/8" river rock / peastone
 
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DO NOT PLACE FABRIC OVER THE MATRIX BLOCK start with larger rocks that won't fall through, then step down to the next size and finishing with 3/4vor 3/8" river rock / peastone
Wow. Thank you!
I appreciate the warning. This is because it will clog, I assume? I must have mixed things up when I’ve seen people use it to protect their pond liners from the rocks.

My “Matrix Blocks” will be modified milk crates.

I also read about DIY bio balls made up of onion netting:

Time consuming but simple.

Thanks for all the replies and links. Great website this is.
 

YShahar

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YShahar

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I decided to add these (bad) drawings to help make sense of my ideas.
Are you going for a naturalistic-looking pond or a formal one? From the drawings, it looks like this would be a formal style pond. If you want a naturalistic pond, you'd need to revise the design a bit.
 
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Are you going for a naturalistic-looking pond or a formal one? From the drawings, it looks like this would be a formal style pond. If you want a naturalistic pond, you'd need to revise the design a bit.
Changing the structure to a naturalistic pond it would be difficult and very costly. Beyond my means. As of now it’s an old concrete pool from the 1970s.

I’m looking at this as a natural pool with many pond aspects. Hoping to have smaller creatures swimming about, but because of the amount of water volume- filtering will become more and more difficult with more and more pooping lifeforms. If the filtration structure, that I have mentioned above, is not sufficient even for smaller fish and frogs (turtles!?!) then I would cut back on aquatic life and stick to water plants. These I would have to feed due to the lack of nitrogen input from small fish.

I’d prefer to be able to swim, but hope to have both plants and a good amount of creatures.
 
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I've also seen people also use plastic screw tops from milk cartons as "bio-balls". Not quite as much surface area, but hey, they're a sunk cost (so to speak).

I used milk crates as the matrix blocks in my intake bay and so far they've proven very sturdy.

Besides milk crates instead of aqua blocks, I see that there are heavy duty plastic pallets out there. These could sit on bricks or blocks to create a void.
 

YShahar

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Besides milk crates instead of aqua blocks, I see that there are heavy duty plastic pallets out there. These could sit on bricks or blocks to create a void.
The worry that I'd have with plastic pallets is that they may not be able to take the weight of rock as well. Milk crates, especially when combined together, tend to distribute pressure to all sides equally. So they actually become stronger when pressed together. Not sure how well plastic pallets would hold u. I suppose you could test them easily enough!
 
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The worry that I'd have with plastic pallets is that they may not be able to take the weight of rock as well. Milk crates, especially when combined together, tend to distribute pressure to all sides equally. So they actually become stronger when pressed together. Not sure how well plastic pallets would hold u. I suppose you could test them easily enough!
pallets are actually a very easy way to figure out the load or pounds per square inch. my concern surfaces not knowing what has been spilled on them and what leached into there cavities
 
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Has anyone used structures outside of an old pool as bio filters? (Either with gravel or bio balls.)

So many videos and websites speak about losing space within the pool. Or excavating out extra space for a bog. But I’ve never seen anyone build a raised structure to hold gravel or bio balls.

The ability to use gravity for the return circuit, for waterfalls and oxidation, seems like an easy pick.
 

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Has anyone used structures outside of an old pool as bio filters? (Either with gravel or bio balls.)

So many videos and websites speak about losing space within the pool. Or excavating out extra space for a bog. But I’ve never seen anyone build a raised structure to hold gravel or bio balls.

The ability to use gravity for the return circuit, for waterfalls and oxidation, seems like an easy pick.
Even if you built your bog inside the existing pool, you could use gravity to return the water to the pool. You'd just need to raise the pool-facing wall of the pond a bit above the rest of the pond. So for example, if you decided to turn the shallow end of the pond into a bog, you could do something like the diagram below:

Pool conversion_web.jpg
 

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