I started a thread over on SF (here) asking what to do with a swimming pool in a house I just moved into.  Aside from the expected answers ("Bunker!") someone posted a link to GardenPool.org, which generated some interest.  So I thought I would start a new topic over here.

In a nutshell, a guy bought a house with an empty concrete pool and built a combination greenhouse/fish pond/chicken coop out of it.  Here are a couple of pics:



















Some initial observations:

1) The guy is definitely drinking his own KoolAid.  Reading the site you'd think he found the cure to cancer.  In the least he's pretending that it's a completely closed loop that only takes in sunlight and air and produces ample quantities of fish, eggs, milk, and vegetables.  Not seein' it.
2) His workmanship is abysmal.  Everything is held together with clear silicone sealant, piping is run haphazardly, wires are strung wherever.
3) I'm not sure about some of his design choices.  For instance, he converts sunlight––>12VDC––>120VAC––>LED screw-ins––> artificial light to grow tomatoes.  This is in Mesa, Arizona - I think there's enough light there to grow plants.  He does later say that he puts up plastic in the winter and shade cloth in the summer but there's no real explanation of anything.
4) The chickens are housed above the fish (tilapia) and their droppings go right into the water, which the fish eat.  Did a bit of research, and apparently salmonella CAN be transported via fish.  So I think that is out.  On the other hand, rabbits don't get salmonella.

My situation varies from his in a couple of places:
a) I live in the Mid Atlantic, with winter temps below freezing for at least 30 days/year.
b) My pool is not concrete but has panel walls, a sand or vermiculite floor, and vinyl liner.
c) My pool does not have a diving well; it's 3' deep at the shallow end, and then slopes to about 7' at the deep end.
d) I have the pool pump, sand filter, and pool heater (heat pump) still operable and in good shape.

So here are my questions:
- What does it take to run a greenhouse in the winter in my AO?  It wouldn't necessarily be for growing plants, but for keeping the fish and bunnies warm.
- Tilapia?  Warm water fish, but eat all sorts of crap (apparently literally.)  Catfish?  Trout would be too picky, I think. (Yes, I'm going to re-read the aquaponics thread.)
- During the summer I'm thinking of covering the hoops with the current pool cover.  It's a mesh cover type and would cover about half the pool.  So the protein section (bunnies over fish) would be shaded over the summer.  The rest of it would be open.
- This pool type typically stays filled to that the walls don't cave in. What is the likelihood of that actually happening? I would cut most of the vinyl liner out except for the well where the fish would be, and wouldn't have an issue with putting in some tie-backs, but would they be needed?  The pool has been there for a long time - I'm thinking 20 years.

Comments?  Anything else to consider?

That kind of pool liner is not made for foot traffic.

I grew up with a large, vinyl lined, pool.  When empty, they don't have the ability to survive very long.  Water pressure keeps things held/pressed in place on the walls, and the sand floor will easily dent/groove/wear if you are walking on it.  The water pressure keeps the weight evenly distributed.

I wouldn't even try it.  

It is a big hole in the ground that was not designed to be empty.  If you pull down the liner, you will need to put up boards and bracing.  I would just back fill the hole and build on top of it instead.

TRG

My intent was to cut the liner back so that it just covered the well where the fish would be.  

A sand floor would be a PITA; I'm hoping for a vermiculite concrete mix like we used when I spent a summer building pools.  It's pretty firm, though not like a standard aggregate concrete.

When you say "boards and bracing", what do you mean?  There should already be wall panels there.  Though admittedly, if they are galvanized steel, there's probably not that much left of them.  The ground water is pretty acidic around here.

Those panels were designed to be pressed against the earth by water pressure.

I doubt they have much structural support with the water removed.

TRG

It actually depends.  The cheaper pools had damned near nothing backing the panels; on the other hand the backfill behind the panels was pretty crappy too, so the amount of ground pressure might not be very high.  The pool I grew up with was like this; the backfill at one corner was so bat that the joint started opening up, including the concrete walk. On the other hand some panels had pretty substantial support, including being tied into the footer and deck.  They wouldn't collapse for a long time.

What I'm thinking of doing is leaving my options open.  Start the demo by draining the pool and cutting back the liner.  Then inspect the walls.  If they are in good shape, leave them be or install some earth anchors.  If not, drop them and the concrete walkway onto the hole and start back filling.

How much area do you have around the pool?  You could just fill it completely, add fish, and build grow beds around the pool.  You'll lose more water to evaporation, but the system will be more stable.

I think that you have a lot of possibilities in creating your own aquaponics system.  It may be difficult to do tilapia since they need such high temperatures to grow well.  I don't have any personal experience though with tilapia, only what I have read about them.  There are apparently some varieties that do tolerate colder temperatures without dying although they would stop growing until the water warmed up again.  If you had an additional heat source ($$$) inside a covered greenhouse over the pool, then you could grow the fish year-round.  It would be very expensive and I would not recommend it unless you had a free source.  I talked to the president of the NH Aquaculture Society and she is using a wood boiler to heat her greenhouse this winter but she has a free source of wood and the wood boiler she also got I believe for free.

I don't know if you were referring to my aquaponics thread, but that's a good start.  Ammonia/nitrogen waste is a huge problem in terms of toxicity.  Rabbit urine/feces is high in nitrogen waste (This is an interesting link I found on the topic with a quick google).  

It would be tricky to allow enough waste into the water to allow for a healthy growth of algae for feeding the tilapia, but not so much as to create an explosive algae bloom that would be unmanageable, even with the tilapia eating it.  The tilapia also produce their own ammonia waste and that has to go somewhere.  If your sand filtration system is working, you could use it to convert the ammonia into nitrate via bacteria growing on the sand.  You would need adequate amount of plants to filter out the nitrate produced, though.  The general starting point is to have twice the grow bed media volume as you have of water in your system to allow for enough detoxification of the water so you can have good concentrations of fish.  If your sand volume is small, it will proportionately limit the amount of fish you can put in the pool.

As far as the GardenPool.org link and the video from your other thread, I'd like to see exactly how much fish and fruits/vegetables they are producing.  I'm not calling BS, but he states in the video that he and his family are "self-sufficient".  I just don't see it.  Also, as you pointed out, chicken manure may contain salmonella and that can end up in the flesh of the tilapia from what I have read.  

ETA:  As Corporal_Chaos points out, you would be better off with grow beds around the pool.  You have a long enough growing season in MD that, while you may need to shut it down partially in the winter, it would be well worth it.  Given your likely water temperatures that you would be dealing with, I would use Channel Catfish or at least one species of catfish.

Yep, that was your thread to which I was referring.  And I agree that he's leaving out some inputs - I just can't see duckweed and plant waste generating enough/proper feed for the chickens.

The problem with turning the pool into a fish pond is scale.  The pool is somewhere between 12,000 and 20,000 gallons.  As you pointed out, rule of thumb is twice the volume of grow bed to pond volume.  That would be 120 cubic yards of media, or about 6500 square feet at 6" depth.  Even if that was halved, it would take up almost my entire yard.    Putting the whole works in the pool allows for some variability and also reclaims some space.  For instance, I could start the pool at 2' deep with appropriate grow beds, get it balanced, and then simply add water when I want to expand.  For that matter the grow beds themselves could resemble conventional raised beds - build a frame out of 2x6, lay it on the floor of the "shallow end", and use the pool liner material to line it.

You're grow bed volume should match your stocking density, not necessarily the fish tank volume.  Also, regardless of how you decide to proceed, consider deeper beds, around at least 12".

The 2' deep idea is smart.  I didn't even think about it.  The volume of media needed for a filled pool would be kind of ridiculous.  By only filling it to 2', you could keep the volume of grow bed material low.  Corporal_Chaos brings up a good point about the volume of media dictating how much fish you can stock, but if your fish tank is huge, you will have a difficult time pumping the entire volume of the fish tank through a relatively small grow bed.  12 to 20K gallons would require a phenomenal amount of pumping.  I could stock several times more fish in my 500 gallon fish tank if I had more room for grow beds.  If I want to keep the CHIFT-PIST type of system, I just don't have the room for more grow beds unless I want to put the grow beds on my garden or cut down some blueberry bushes.  I don't think I'll be doing that.  I'm happy with my current set-up and it's a lot of work to redesign it, especially since my grow bed media is the relatively dense/heavy gravel.  It's very inexpensive but heavy to move around.

Going in an entirely different direction, you could consider a simple pond system.  Your fish stocking density would obviously be a lot lower, but you could try a few different fish in the "pond" and see which one does best in your area.  You could do floating watercress rafts over, say, 1/4 to 1/2 of the pool.  They would give  a place for the fish to hide under during the day and complete the ecosystem.  You could use goldfish or maybe even tilapia to control algae.  Another great way to control algae are Daphnia.  I wrote about them in my thread and I can mail you some if you end up going this route.  The advantage of a pond is it's very simple and would require a lot less work.  

I've never had a pool so I'm not familiar with the sand filtration you refer to.  Can you put gravel in there?  I'm thinking that while you would not be getting a lot of detoxification of ammonia to nitrate conversion, it would be some.  Can you also get pictures of the pool?  We always love pictures.

You wouldn't need to cycle the entire volume of the fish tank through the grow bed every hour either.  A larger volume of water means it would take much longer for nutrient concentrations to reach dangerous levels for the fish, especially if one was stocking to grow bed volume and not fish tank volume.  Cycling the fish tank volume once an hour is more of a hard and fast rule meant to be coupled with the 2:1 grow bed to fish tank ratio and maximum stocking densities for such.  Remember, the solution to pollution is dilution.  

Here are a couple of threads over at BYAP that detail using pools as fish tanks:

This one is more aquaculture than aquaponics;
This one is more along the lines of straight aquapnics.

A smaller pump would work fine; it's size would depend on how densely you stock your fish and their aeration needs.  Personally, I wouldn't bother with using the pool's existing pump and filtration.  Doing so would cost more in energy and effort than it would be worth, at least to me.  Deep gravel grow beds like the Rubbermaid stock tanks would be ideal for this application I should think.  Another advantage is, you will have plenty of fish tank for expansion, so you could just add grow beds and fish as time and money allows.  The large volume of water would also create more thermal and nutrient stability.  I don't know what your climatic conditions are like, but a large volume of water may even allow you to run trout year round, perhaps with extra precautions like shading in the summer and additional aeration.  Rapid temperature swings seem to be more harmful than the temperatures themselves, and a large volume of water helps prevent rapid swings.  If not trout, channel catfish or blue gill would probably be best, as they can survive colder temperatures than tilapia.  I don't think tilapia would be a wise choice unless you plan on building a full green house over the pool (and grow beds) and have a plan for heating.  TCLynx over at BYAP is in Florida and even she had trouble keeping water temps high enough for her tilapia.  

Bottom line, do some reading over at BYAP and you quickly come to the conclusion that the people with larger volume fish tanks experience fewer problems.  Again, the solution to pollution is dilution.  If there is any concern about your pool's integrity when only partially filled, using it completely filled as a fish tank is an option.

Very interesting - especially since one of the posters in the second thread lives about 20 miles away from me.

The idea of more volume with. Fewer fish and deeper beds is interesting.  If I put the beds up against the walls they would help with wall stability concerns, though I'm not reallty that worried about it.  I think I'm going to pull the cover back a bit and take some dimensions.


Posted Via AR15.Com Mobile

Wasn't this setup featured on doomsday preppers?  It looks familiar.

Pick up Sylvia Berstein's book on aquaponics before you try that project. Nothing about the setup seems particularly dialed in.

Somebody mentioned using rafts for the plants in the other thread, i.e. the fish tank as the growth media. What about turning that on it's head: drop a few cubic yards of gravel into the well of the pool and circulate the water down through the gravel via the existing bottom drain? It would lessen the need for media in the grow beds, provide an anchor for some types of aquatic plants, and allow culture of more species (I'm looking at you, tasty tasty crawfish). it could be back washed periodically to kick out the waste solids, which could then be collected and used for conventional garden fertilizer.

ETA: Apparently I just reinvented the downflow gravel filter.  

Oh, and sand filtration is just an older style of pool filter.  Just a cannister filled with sand through which the water is pumped.the one for my pool is about two feet in diameter by thirty inches tall. It provides mechanical filtering and a little bio-filtering, but not nearly enough to deal with fish waste - only the occasional kid pissing in the pool

Posted Via AR15.Com Mobile

I don't think it matters how you set it up.  As long as there is flow through the gravel, then bacteria will colonize it and you will get ammonia to nitrate conversion.  You can do both ie. watercress floats and gravel filtration because you still need a 'sink' for all the nitrate once it's produced.  One thing that would concern me is any obstructions.  If you don't have access to all the tubing, you would have a difficult time clearing a plugged tube.  As long as you have good screening of material so it can't enter the bottom drain, only water gets through.