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PostPosted: Feb 17th, '09, 00:19 
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Hi Everyone,

For a long long time, I've been wanting to convert my inground swimming pool (10,000 gallons) into an aquaponics systems, growing fish for food and using the water from the cement pond to nourish vegetables and other edible plants (in tanks around the perimeter of the pond). This year, it's happening with a lot of help from staff at a local aquarium store, people who work for fish hatcheries, aquaculture specialists with the cooperative extension service, and hopefully some of you. My system deviates a bit from the standard aquaponics model in that it's outdoors in a temperate climate (Arkansas) and the fish will be raised in a cement pond rather than a tank.

Here's where things stand. As of a week ago, the pond, which has had no input of chemicals since the fall, had a high ammonia level. I removed leaves from the bottom, added Prime and a Parrot's Feather aquatic plant which is winter hardy, and started aerating. Then I got 3 feeder goldfish and introduced them to the pond over a 7-hour period to adjust for the radical difference in water temperature and chemistry. They are fine. This morning I bought a pound of minnows from a fish truck at the local Farmer's Coop. After they adjust, I'll add them. As temps warm, I will introduce more plants and the dominant fish species, which I am still trying to choose.

I've discussed which fish to stock with a lot of people and am now leaning toward tilapia, if I can find them close enough and at a decent price--a big question mark. But easier for me apparently than for many of you, as there are suppliers in Arkansas. (Note I am in the Ozarks, which is cooler than the delta region.) Prices seem to start around $6.00/pound.

The tilapia would have to be harvested in the fall, as temps decline (the growing season would start sometime in May and end sometime in late Sept/early Oct). A batch system is a good thing because it gives me a chance to clean out muck from the bottom, but also a problem because I have to get bacteria going again and the system normalized, not to mention wasting water. I might be able to raise trout in the winter and return to tilapia in late spring--a seasonal rotation.

The other options are bass or catfish. I've considered and ruled out crappie because they breed prolifically and I'm likely to have 10,000 fish at 2-3" come harvest time. Hybrid bluegill are another obvious choice but apparently they bite swimmers and I have two young boys who would like to jump in the pond to cool off. Bluegill, I am told, are also hard on plants, and I would like to have a lotus and water lilies in the pond (believe it or not, they are edible too.)

If anyone has suggestions or advice, please respond to this post or email me at skyper [at] mac [dot] com.

All the best...
Rebecca


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PostPosted: Feb 17th, '09, 03:18 
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Seriously, this cant be healthy.
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Hi there and welcome!

Swimming pools being turned into AP systems definitely can and has been done.

Your big challenge will definitely be with temperature. I'm likely to advise against the tilapia unless you can get advanced all male fingerlings and have 80 F water over the entire period you have them. I have an outdoor system in Central Florida and had to put some money into keeping my system water warm enough this past month just to keep them alive. They really have not grown much since November. They barely eat at water temps below 70 F and even at 70 F they don't grow very fast.

You mention that your area is cooler, you might even think about trying to do cool weather fish year round? It would all depend on hot hot the hot weather really is and with an in ground pool as a tank, it might not be that difficult to keep your water temps cool enough over summer.

I don't really know much about tank culture of bass or bluegill. I've swam in plenty of lakes with bluegill, perch, and sunfish and never been bitten by one but that was in a lake. I have had goldfish in an ornamental pond nibble at my legs while I was working on the waterfall, darn that tickles, but those fish were not more than 6 inches long.

I don't think I'd be all that comfortable swimming with the catfish cause I'd be afraid of the barbs though the catfish are generally scardy cats in my experience. Actually, jumping into the pool with the catfish would probably stress them out.

I don't know that jumping into the pool with the tilapia would be all that refreshing since 80-90 F water is what you will be hoping for to grow them out fast enough.

If you want to grow lotus and you wind up going with a fish that is hard on plants, perhaps you could make something of a plastic mesh cage around the plant area to keep the fish out. I've also heard that lotus are edible but have had trouble finding plants or seeds for the tasty varieties.

I think your biggest challenge is going to keep stuff from freezing on the cold winter nights. I really don't think you want to shut down completely over winter since re-starting the bacteria each year during the cool spring will set you back a couple months each season. Part of the benefit of an AP system is having a mature system. Even if you only have plants in a few grow beds under some sort of "greenhouse" for the winter and simply insulate and cover the others to keep them warm enough that the bacteria can survive at a reduced population. Then you could uncover the other grow beds as the weather warms up and up the feed for the fish to ramp up production and expand the bacteria population as you plant out the beds etc. Just have to work out how to keep pipes and siphons from freezing.

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PostPosted: Feb 17th, '09, 11:12 
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Welcome aboard, Rebecca,

The pool idea sounds really fun. If you were to go for tilapia you might be able to have a portion of the system that consists of a greenhouse, growbed, and heated tank so that you can get a big headstart in the spring. Once the pool warms enough, maybe the growbed could be linked into the larger system of pool and other growbeds. If you keep the growbed damp over the winter I think that some bacteria would survive, so you would have a much shorter cycling time even if you had no winter fish.

If pools normally are at least 75degF around there for four months or so you might be able to get some good fish and you could continue to harvest them until water temperatures are down to 55degF. It could work...

I think you could rig up some intake (from pool drain?) that gives the growbeds water from a debris collection point in the pool as letting the stuff build up in the pool is not the best for water quality and the plants/worms would love the nutrients. Seasonal cleaning of sludge sucks.

I think I have similar concerns about channel cats and swimming, but maybe if you had some shelter for them they would simply stay out of the way. I know they don't want any trouble and would prefer to hide.

For winter crops the hoop greenhouses work well. Lettuce, cabbage family, other cool crops. You could even put a winter greenhouse over the pool to help warm it several degrees.

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PostPosted: Feb 17th, '09, 11:48 
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I agree about the seasonal cleaning comment. While cleaning out a pool or ornamental pond seasonally might not be so bad.

Cleaning out anything that gets large quantities of pelleted aquaculture feed is gonna be much nastier.

Best to design so that leaves and fish poo/uneaten feed clean up is regular and automatic rather than monthly or seasonal.

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PostPosted: Feb 17th, '09, 21:25 
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I love tilapia, but they are not going to eat enough to grow fast until 80 F. I dont know if a pool would even reach 80 degrees. Trout may be a better bet as you would have more time to grow them out. 6 months for tilapia might be pushing it; even at 80.

Good luck, and welcome to the madness!

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PostPosted: Feb 17th, '09, 21:55 
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I got my tilapia in May (mixed gender) and a few were pretty large when we got them but most were small. We ate a few of the large ones pretty quick but many of those smaller tilapia are still too small to eat and it's been 9 months. The males definitely do grow faster though.

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PostPosted: Feb 17th, '09, 22:04 
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DanDMan wrote:
I love tilapia, but they are not going to eat enough to grow fast until 80 F. I dont know if a pool would even reach 80 degrees. Trout may be a better bet as you would have more time to grow them out. 6 months for tilapia might be pushing it; even at 80.

Good luck, and welcome to the madness!


I'm sure you guys are right: mine are about 1lb (.5kg) after a year of very imperfect conditions. The notes I have seen say it takes 6 months at 86degF (30degC) to reach that weight (.5 kg), but that must be under optimum conditions. Still, one can eat them smaller and it is really useful to have fish that love algae: it might help avoid the troubles many have and the need to shade the water.

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PostPosted: Feb 17th, '09, 23:59 
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I want to thank all of you for taking the time to advise me. Your help is much appreciated.
The main concerns I am hearing are: 1) water temps are likely to be a problem for tilapia; and 2) seasonal batch harvesting is a hassle and counter productive.

Let me address both of those in more detail. First, water temps. The ambient temperature in Fayetteville averages 75 or better for only 3 months. However, my aim is only 1/2-3/4 pound. People eat perch that size all the time, so I'm wondering if there is any reason not to downscale expectations. Are they more of a hassle to clean?

There are interventions to compensation for the climate. Maybe by the fall I'll have a straw bale greenhouse on the property in order to overwinter some brooders and get a head start next spring. Or maybe black plastic over the pool to extend the season? Alternatively, I can reconsider fish species, which I am certainly willing to do. From the various discussion on this board, it seems like getting a good species of fish may be the most difficult aspect of aquaponics.

Now to the batch system approach. I, too, would prefer a year-round system. But if I stay with tilapia, how else does one harvest them? The pool is 7 feet deep, although if I rely largely on rainwater, who knows how deep it'll actually stay through the summer. A net with poles on each end might remove a lot of the tilapia. But then there's the water quality issue. Artificial tanks do need periodic cleaning. I can attach the pool vacuum and see how well that works. Maybe it'll be sufficient.

I am going to talk to one of the coop extension aquaculture specialists again about fish species and will fill you in on that conversation.


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PostPosted: Feb 18th, '09, 00:15 
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Can you get all male tilapia there without special aquacultural permits? If not, then you might think about raising the tilapia in a cage floating in the pool, this would certainly make batch harvesting of them easier. I am raising my tilapia in a net and pvc cage within my large tank to keep them from breeding uncontrolled. If the tilapia are busy breeding, they spending energy which would otherwise go to growth and the females are not eating at all while they are brooding eggs.

You still want some type of fish swimming outside the cage to clean up the food that escapes the cage, I'm using a few channel catfish for this purpose.

I suppose cage culture might also work for other fish that you wouldn't want biting swimmers but I kinda doubt that a fish would attack a swimmer unless the pool were very heavily stocked and fish underfed or if a swimmer were to step on the fish. Main problem with cage culture is you need to feed each cage and make sure that there is plenty of aeration and water flow through the cages and feed often floats out of the cages depending on the size of feed and size of netting.

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PostPosted: Feb 18th, '09, 00:30 
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Quote:
my aim is only 1/2-3/4 pound. People eat perch that size all the time, so I'm wondering if there is any reason not to downscale expectations. Are they more of a hassle to clean?


I have, infact, cleaned and eaten a half pound tilapia. I makes a nice small portion of meat for a one person. So theirs no reason you can't do that. If thats what works for your environment the go with it.

For me, I really dont like gamy tasting fish so tilapia is my preference. They are fun fish too. Breading really does slow the females growth. So I suggest grading them if you do not have all male; or perhaps get more than you need so numbers make up for size.

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PostPosted: Feb 18th, '09, 01:22 
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Welcome Rebecca!

My opinion is to choose a fish that would love your water temps that occur six months of the year, rather than one that would barely tolerate the temps that occur three months of the year. A pool that big will be a pain to get up above 80 degrees where the tilapia will be happy and grow (unless maybe you erect a covered frame over it??). If you think you can do it through maybe a pool blanket or something without pumping a ton of electricity into it then maybe. Speaking to a permie though it might be more sustainable to choose a species that loves the water temps that naturally occur there without additional heating.

I've been keeping tilapia for the last few years and the heating requirement is pushing me ever so slowly to switch to something else, maybe trout. I would love to be able to grow something that doesn't require any heating at all for most of the year. For example, this time of year we have a lot of sun that would grow some happy plants but the tilapia are a no-go until probably mid-June. (The trout would likely be harvested by the end of June though unless some cooling and shading mechanism were added, and they are not tolerant of pump and aeration outages so its definitely a trade-off).

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PostPosted: Feb 18th, '09, 01:43 
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I find that catfish are not gamey or fishy tasting (of course the cook usually cleans them and they go immediately into a salty ice water bath for a while before being marinaded over night and smoked or grilled the next day) at all but if you don't like the texture (dense flesh) of catfish then I see where some people choose tilapia instead.

And Yes, people eat perch, blue gill and sun fish that are small all the time, ya just gotta clean a lot more of them for a good size family meal and we have eaten 1/2 lb tilapia here since it is sometimes difficult to only catch the large ones. Of course the smaller the fish, the less likely you are to filet it and then people have to cope with the bones on the dinner plate.

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PostPosted: Feb 18th, '09, 05:36 
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Pumping through black pipe is an easy way of heating your pool. 300mtrs of 13mm on the roof allowed me to adjust the temp by 10degrees over winter in 55kl pool. You can give the pool a vacuum every now and then. With enough fish they seem to keep solids off the bottom. And adding a swirl filter will help in catching some of the solids. Main problem with pools is in the amount of media you need for the bacteria. And the volume of water that has to be pumped.

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PostPosted: Feb 18th, '09, 21:38 
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I am still waiting to review fish species with the Coop Extension agent; he's at a conference. For any Aussies reading this, the US has a system of land grant universities with ag programs. The Cooperative Extension Service is an adjunct set up to transfer knowledge from the ag programs to farmers, aquaculturalists, and the general public. It's pretty much an industrial ag model, but the agents are wellsprings of info.

I haven't seen a source of male tilapia but that's one of the questions I'll ask.

TCLynx, you mentioned that it's best to design so that clean up is automatic. How would you go about that?

Dufflight, you touched on the same issue, suggesting that enough fish might keep sediments stirred up. And you raised other good issues. How do I scale elements of this system to achieve stability? I hope to approach this in as low-tech a manner as possible with minimal input of energy. I want to have some plants in the pool to supplement biofiltration. Ideally, the plants would be mostly edibles but duckweed and parrot's feather will have their place. Hence, there is a need for compatible fish--ones that eat each other, daphnia and other microlife, various kinds of algae, insects and larvae, muck and feed.

Other parts of the cleaning system are already in place: 1) a pump that pulls water, mostly from the surface, through a skimmer with a couple of baskets en route to catch debris, through a sand filter and back into the pool (aerating in the process); and 2) a vacuum tool to clean the bottom of the pool.

Around the pool, I want to place some metal or plastic livestock water tanks. They are 2' deep and either round or oblong. They have an outlet at the bottom that can drain back into the pool. I'll need an additional pump of some kind to move water from the pool (what depth to suck from?) into the tanks. I have no idea how much media are necessary for the bacteria or what volume of water to pump. Similarly, I have no idea how many fish I'll need to obtain a sufficiently rich feed for the vegetables.


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PostPosted: Feb 18th, '09, 23:26 
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for automatic cleaning, the skimmer baskets should take care of leaves but you will have problems with your duckweed and any other floating plants getting sucked in too. You might be better off growing duckweed in a separate tub or tank since any fish that will eat it, tend to eat it all up anyway so you would have trouble growing it in a tank with fish that like it.
You may find you need to adjust the balance between the pump intake at the bottom and the surface since you want to suck in fish waste. As to automatic cleaning, well you still need to manually clean out traps and skimmer baskets and such but that should be about as regular as feeding the fish and harvesting plants for dinner.

Ok, how much gravel beds to use. Truth is, that should be related more to how much fish you will stock more than how big the pool is.
Now I really need to make myself a cheat sheet for this since I can only ever remember the metric rule of thumb.

3 kg of fish (that is intended grown out total weight of fish) per 100 liters of grow bed (that is total volume of grow bed, not worrying about % of water to flood it or anything at this point.)
Now let me look for the conversions.
Ok, so I'm rounding a little bit here but lets call it 6 lb of fish per 25 gallons of flood and drain gravel grow bed.

That amount of fish should be able to support as many veggies as you can grow in that amount of gravel once your system works up some nutrients. It will take some patients.

It does not matter so much how big the pool is, it matters that you provide enough filtration for the amount of fish you grow. Granted, with your huge amount of water, it will take longer to build up useful levels of nutrients but just think how stable your system should be.

On a side note, your sand filter (provided it gets used and back flushed very regularly) will provide some extra filtration for your system. It is important to keep it flowing, if for some reason you shut it off for several days and then put it back in line, be ready for a nasty smell in the water going through it since it only takes two days of it being shut off to become totally anaerobic. I know, I have a sand filter hooked to my system (got it fee) and once you start using it, ya gotta keep it flowing.

Another note about water plants, they will use a fair amount of nutrients and they often use them before the nitrogen cycle gets it's hands on them so you might want to avoid adding many pond plants into the pool until after your initial cycling of some grow beds, that way you can be sure you get a good bacteria colony going before throwing too many variables in.

Anyway, Perhaps once things get cycled and such, perhaps you can figure the sand filter and pond plants might count as another grow bed in your stocking figures but I don't know How "big" they would count for or how much extra fish you could stock based on their existence in the system. Probably best to not count them in the initial season's stocking anyway and slowly ramp up production as you see the system is able to handle it or not.

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