Aquaponic Gardening

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Hi everyone! This is my first post here. I have a very green swimming pool that is roughly 20k gallons kidney shaped and has not been in service for 4 years. There is a good amount of sediment at the bottom that I have been removing by way of pool net over the past few weeks and it appears that I am making progress. I would say that 90% of this is dead or dormant algae, and the water as you would imagine is quite green. There are mosquito fish in there that have been happily living and reproducing for several years (and controlling mosquitoes effectively)

I have convinced the owners of the pool/pond (my parents) that the best thing to do is to create an oasis using natural methods and the like, and they are onboard so long as it doens't cost too much or become too much in the way of maintenance.

Some more relevant info is that we have a very steep slope above the pool as well as some area below the pool, either of which could be used for growbed/sump areas.

My idea at present is to pump the water from the skimmer up to some grow beds on the slope (southern facing) and then cascade this water back down to the pool perhaps through a solar heating panel and/or a uv filter.

Here are some questions for you all...

1. Will I be able to remove the algae without draining the pool? I am dilligently working to remove the scum from the bottom and I believe that I can get most of it, however, I am unable to stop the individual cells from going back into the water through the net, and at some point it will be necessary to kill it (shock with bleach) or UV filter it or something. The plan right now is to get as much out as possible, and then shock everything to kill all the algae while constructing the beds etc. The reasoning is that we cannot afford to crack the pool from groundwater if we empty it, and it is very expensive to refill it if we empty it. What would you do?

2. Does my plan to use the slope make sense? How much media will I need to filter this much water? I am thinking that I can construct some grow beds that are individually plumbed and feed directly back to the pool, or make them go from one to the next all the way down before flowing back. Is one design better than the other? Keep in mind that in the end we plan to have minimal fish for the purpose of controlling bugs and algae (tilapia or cats?), providing some fertilizer for the plants, and maybe some pretty ones for looks/eats. We do want to swim in the pool during the summers.

3. There is an existing sand filter. Is this useful in any way?

Thank you! Any and all comments/ideas will help greatly. I am curious about the UV filters especially at the moment, and any experience anyone has had with this type of thing.

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I have some of the info you seek.I already have one working rely well Paul

Hey Nik!

The first rule of Aquaponics is:  There are no rules! 

Yes, this whole thing makes perfect sense. 

Your current situation seems to be a full pool with some nastiness if I gather correctly.  If that is correct, right now you could turn on the pump and just start throwing in fish after checking the ammonia levels, none is good; 0.50ppm is going to be about the limit; above that would mean a partial water change.  Feeder goldfish are cheap if brought in quantity and they will help to mow the "pond grass" in the near term.  The grow beds on the hill idea works.  You will have tons of capacity after you get the fish density up some. You should already have plenty of bacteria in your system, adding a place for them to interact with the flow of the water in some sort of inline media will be beneficial to scrubbing the water.

What I see as your biggest issue is going to be filtration.  You may want to plumb around the sand filters.  Pool sand filters are meant to be fine particulate filters.  You will have large particles and rapidly filling filters which is okay if you don't mind back flushing the filters regularly, as in daily (most likely).  I removed the cartridge completely out of my filter and left it inline.  I now use a combination of evaporative cooler pads and sediment tanks for filtration prior to the flow entering the grow beds.   I have also seen mesh lined milk crates in plastic storage bins used effectively to reduce the particulates in suspension in this manner. I could barley see into my pond before I made the previously mentioned filter, now the pond is gin clear.   The UV filters kill all the necessary bacteria, you will want to let nature clean your water as designed by the great creator.

There are several types of growing options you will have available to you.  First of course, you can do the normal raft or media beds all while using the hill to return the water to the pool via gravity.  You  can also use a version of vertical farming where the NFT (nutrient film technique) is utilized by plumbing 4" plastic pipe, rain gutters or troughs with plants in small pots across and down the hill using gravity to return the water to your pool.  There is also a little discussed technique where your grow beds are just hung off the edge into the pool.  If you hang your grow beds from the pool edge your fish may eat the roots, protection may be required from fish with munchies.  The other drawback is being on your knees to service the beds. 

A big deep pool in a colder temperate climate will allow you to have some additional flexibility in the aquatic animals to choose to be invited guests. Trout, Tilapia, catfish, shrimp and more are all reasonable choises

Bare in mind:

The pool's annual water temperature. 

Using what nature provides is best: i.e. light, temp, water

You may find that trout, catfish or shrimp are a better choices than the standard tilapia.

Your fish will generally like higher pH than your plants, so if the plants get yellow leaves you will need to consider pH adjustment.  

Your system will tell you if it is out of balance; too much ammonia -- add plants; wimpy plants -- add fish (generally speaking).

Start by getting a good water test kit so you can test for ammonia before adding lots of fish because they won't survive high levels of ammonia.  You are going to have a very big system by most hobbyist standards.  I suggest you spend the time to read this thread, as it will give you a pretty good idea of what is going to happen and how one person dealt with a large pool of water/fish capacity.  (

Good luck, keep good records, keep us updated and let us know when your pool is going to be in Sunset Magazine!

BTW: your pool should be clean enough to swim in (like a lake) by the end of the summer if you get started right away!

all the best,


wish this natural pool were mine...

Completed pools - A classical pool in an historic landscape setting, Cambridge (4)


Thanks so much for your advice. All of what you have said corroborates everything that I have been reading about ap.

We are hoping to swim in the pool this summer. With that in mind, I am considering the removal of the algae by mechanical means first with the net, and when that gets impossible (due to their small size) to turn on the filter and do as many backwashes as needed while also shocking the pool with bleach and using a flocculant.

I know that I am in dangerous territory talking about killing all those microbes on this forum, But the better results that I can achieve in the near term will translate to my allowance to proceed with the "natural pool" project in the long term.

Raising fish and plants is not the primary goal of the pool owners, rather a low maintenance system for keeping the water clear with low $$ inputs and high aesthetic value is what is desired. My goal is to raise fish and plants, so you can see the rub.

When I build the growbeds out that will eventually be filtering the pool, do i need to match the surface area of the pool with media surface area, or what? I have seen many different ratios thrown around, and I certainly will not be able to attain a 1:1 volume media to water for this project, nor even a 1:4 for that matter. I was hoping that I would be able to get by pumping at least half of the pool volume per day through the beds, which means about 400 gph for 24 hours. My idea was to build concrete beds about 2 feet wide by 10 feet long and 2 feet deep on the hill giving me a surface area of 20ftsquare per bed. I would then need about 10 of these to reach the ratio of 1:1 surface area, which I think is the rule of thumb for natural pools. These could be planted with ornamental plants, and should be able to handle the waste from some mosquito fish and a few others, as well as some swimming in the summer months and the leaf litter from the trees.  

This calculates to 40 gallons per hour per bed. I think that it seems reasonable to do that, am I going overboard or missing some things that I should consider? Maybe the top bed is media free and can act as a settling tank?
I was thinking of having the beds filter separately, like to have the pump split with a line to each one. Would it be better to have the water flow through all of them in-line to clean the water more, or what?

Thanks guys!

Hey Nic:

Glad I didn't lose you. 

step  1.  The goldfish will plow through the algae quickly if you don't feed them.  After you wear yourself out with the dip net,   just turn on the pump, check the water quality and add the fish!  Really Nik save your effort, time and money on the superfluous chemical routine and apply it elsewhere in your project.  You should be able to get a 100 feeder gold fish for 30-40 cents a piece. They are small, but they will grow fast in a big pond with lots of food.  Don't worry 100 is not very many in a swimming pool even when they are full grown.  Get the good water test kit that checks, pH, ammonia, nitrates and nitrites for about $30. While filtering dump water until the ammonia is 0.5 or less, then add fish. See if the fish store has pond plants too; start small they grow fast, might is well save a trip...

step 2.  Hack up the existing pool plumbing (lol).  You will want to use the main drain after the water is clear but using the main drain will be a nightmare in the early stages.  You may need to add in valves to shut off the main drain.  Many pools are set up this way originally so check before you get out the sawzall! I need to shut off the main drain before vacuuming from the skimmer inlet on my system.  This change happens before the pump.  Just use the skimmer to suck water off the top for now. After the pump, eliminate the sand filter and run the water through a large particulate filter with a deep sediment tank similar to this photo:

First off I would not use clear (sunlight grows) and I would chose higher quality but this clear box allows for a see through view.  Make some sort of filter holder (brown lines) The media is shown in blue.  You will need to rinse the filter media regularly in the beginning so make it's removable.  The outlet will need to be larger than the inlet because it is under pressure, you will probably need make several filters like this for the volume of water the pool pump will provide, which is a good thing    I would start with 2 or 3 filter boxes to slow the water allowing the sediment action to happen 1- 1/2 inlets and 2" outlets which just dump back into the pool at this stage.  Later, you can move the filters around to the separate grow systems you are going to create after we tame the pool.

I have included a photo of what I used as filter media but most anything will work if it is inert.  The blue stuff is synthetic evaporative cooler pad, which your local Home Despot or bLowes will have access to, if they don't stock it.  The white grating was found at HD in the lighting section.  While you are in electrical; pick up several 1-1/2" (inlet) and 2" (outlet) conduit nuts as they will screw all the way on to the male threaded PVC fittings you will use as bulk head fittings in the plastic box.  Pick up some aquarium grade silicon while you're buying fish to seal the fittings. 

consideration 3. grow media area in your case should be sized by the fish load.  The flow volume will have to be higher so the plants still have access to the same amt of nutrients if you choose to limit the fish load.

consideration 4.  this is a symbiotic system both the owners and user goals will be met at the same time. 

>Raising fish and plants is not the primary goal of the pool owners, rather a low

>maintenance system for keeping the water clear with low $$ inputs and high

>aesthetic value is what is desired. My goal is to raise fish and plants, so

>you can see the rub.

Just remember to address the aesthetics as you move forward.  ie:  put the filters (above) in nice redwood boxes next to the pool instead of using say - blue barrels...You could even make covers with a large hole in the top to hang pots in the water with ferns billowing out!  Sounds nice already! You may want to consult the Feng Shui handbook before starting...

Always think about how everything will look when you are done... parallel pipes everywhere, watch the glue smears, pain the pipes to coordinate with the house trim, whatever it takes to keep the funding flowing.  You may even want to plumb the filter boxes in parallel to clean up the plumbing; make by the main line go into just one box and small tubes between the other filter boxes. Looks clean that way!  Place the inlet into the filter box so the pipes do not show from the patio and hide the return outlets since they will turn green with plant material right away. Your benefactors will appreciate your attention to detail...

consideration 5. worry about the grow beds after you get the system cycling.  But yes, you can and will create a beautiful ornamental garden which many people will enjoy if you address the aesthetics as you go along.  Consider adding a waterfall/stream feature to oxygenate the water without adding additional equipment.

gratuitous photo:

Below is my fish pond/FT that is residence to 30 large and 5 small fancy goldfish,  5 full grown tilapia, a dinner plate sized turtle named Sheldon and a couple hundred mosquito fish.  There is a waterfall with stream with 3' of total drop  over 10 feet with 5 drops and small river rock strewn off to the left, I don't have to add any O2 enrichment even at 110 degrees today.  The Arizona sun is pretty brutal so I have added a shade screen over the pond this year for the first time.  The lily pads really like the shade as they have now covered the pond and usually only cover about half the surface at full growth each summer.

keep me in the loop Nik, good luck!



Hey Nik! 

How about a couple "before" photos? 

Now how picky are the parents about how it looks?  I mean, what do they conciser acceptable and what is ugly to them?  Find out since some thing cost a huge amount to make all fancy and if they think a 100 gallon rubbermaid stock tank full of lovely plants looks nice, then that is one of the easiest ways to go for filtration beds where you can get lots of filtration and a comfortable height bed just by plumbing it in and filling with appropriate gravel.

No, you don't have to have a 1:1 ratio.  The biggest trick will be figuring out how much you need to pump and circulate water to keep it nice.  Some simple water falls with lava rock in them will provide a huge amount of filtration and aeration.

Since you already say there are mosquito fish living in there. I would caution you NOT to shock the pool using bleach or chemicals since then you would have to remove all the dead fish and start the bio-filter over from scratch and that probably would take you all summer.

Quickest bio-filters you could do might be to get some big tanks (IBC's or 300 gallon stock tanks or a free spa off craigs list, whatever) and you pump into one to use as a settling tank like jim mentioned and then into the next one that you fill with shade cloth and/or bird netting or whatever to act as your "net tank" then do a waterfall back into the pool.  Those filters should be skirted to look nice and as you look at your space, you figure out if you can have them also feed your "grow beds" or if the grow beds will get fed separately.

Getting algae up into a media bed to die off and decompose in the gravel has a similar effect to using barley straw to inhibit algae.  Unfortunately, if you have high nutrient levels and sun hitting water, green will still tend to be the color that will show.  But hopefully if you can get enough algae decomposing in the filters, you will mostly have surface algae instead of pea soup green water.  My systems have always had nice clean water but surface green and string algae still tend to grow where sun and water meet.

Thank you all so much for your advice, i really feel like I am getting somewhere with this!

Before pictures to come...

How many 100 gallon rubbermaids might i need for this?

I have a ton of redwood stakes that I could "skirt" around ugly stuff to make it look better.

Do i need a settling and net tank if i had lots of gravel beds like this?

would a settling tank as described really settle out a lot of the algae?

How would one clean out a "net tank" I am finding right now that the algae at the bottom of the pool only clumps because there is so much of it, and it is able to be scooped up with the net. so i am weary about the net tank because of that, or is the net more of a biofilter that just has lots of places for bacteria to grow? Either way a lot of this biomass needs to be removed, or killed (thinking about a uv filter) and removed. Once there is an acceptable amount, then i would be happy to let it be and try to outcompete it with plants and fish that would eat it too. (Will goldfish really eat algae? only from the walls and the surface right?) Are catfish good for this?

I am thinking that i will need to filter out the algae and remove it from whatever filter is used as well, because there is a lot of it.

For those that are interested, my friend is something of an algae entrepreneur and he brought out a team to try and get a bunch for making into algae oil. they tried pumping it through different sized netting which didn't really work, which is partly why i am concerne about trying the Net tank. My friend has access to an algae separator that spins the algae out of the water, but it is being used right now for another project and i cannot access it ARRG.


Hum, now many 100 gallon rubbermaids would you need?  That is a hard question.  But one of the reasons I recommended getting the other filtration set up first was that you want to try to clear the water but you will probably not be able to afford enough gravel to make enough gravel beds to really handle the algae or leaves likely to form in a pool or fall into a pool.

The net tank is more as a bio-filter but you are right in that they can be kinda nasty to clean.  I think the normal method for cleaning net tanks would be to mount something like a hose reel that you hook the netting to and "reel" it out of the net tank as you hose it off and then pull it back off the reel into the tank.  I've never personally done this and it doesn't sound especially fun to me.  But as a way to filter lots of water cheap, the settling tank then net tank are probably your quickest, cheapest options.  If you make sure to cover (block all light) from those tanks they won't grow more algae and may collect a good deal of your algae from the pool.

Then you add the 100 gallon grow beds as you have time and the funds to add them.  Get barley straw to help combat the algae.

One of the biggest issues with algae is that it is so difficult to "de water".  that is why they like spirulina so much, it's form makes it easy to filter from the water.

Aesthetics?  they are in the high rent district north of SF...

Yes, gold fish love algae.  Try step one above if it doesn't look like it's working you can always try killing everything. 

I had what you have on a smaller scale, step one/two worked, the water was gin clear within a few weeks...

Pictures...they help immensely in understanding the problem

Hi guys, here are the pictures as promised.

As you can see it is difficult to see through the water, more like a gin and juice.

Shallow end you can see the bottom and some of the gunk that is down there. Whenever I stir it up, some ends up over here and I push it back to the deep end for scooping out.

Here's two hours worth of gunk (35 gallons)

Close up after a few days in the sun, a lot of water has evaporated from the surface.

Plants I put in pond baskets weighed down with rocks. The leafy one is sticking upright in the sun today after its initial shock.

Mosquito fish

Overview shot showing the slope of the hill. Prickly pear will be removed...

Yes the rents are high here! We live in the one small house in the area, but we have a HUGE backyard. It is a bit of a trek down to the pool. Aesthetics are very important, although I think anything will be an improvement on nothing, that is not the way that everybody feels. Any tubs, tanks, barrels or otherwise will have to be hidden which is fine if you consider that we don't want the sun on them anyway.

This weekend I did a little bit of foraging and got some water plants from a local waterway. I Installed them on the stairs. I also took a water sample into the fish store and they do free testing there. So I found out that there are no nitrites nitrates or ammonia, PH is between 7-8, so with the 1-200 fishes in there already, there must be plenty of good bacteria, and I imagine that the algae is eating all those nutes. Secondly, I asked about getting about 100 feeder fish and the guy told me that it would be pointless to have them eating algae because of the scale involved that they would not make much of a dent under a count of 500 or so. I disagreed, but allowed him his say, I will likely go in and get the fish anyway, but I was considering that I might want to look elsewhere for better fish for the job, considering also that there is no other purpose for goldfish other than eating algae, and possibly becomming food for a bigger fish or turtle or something down the line (yes I am already dreaming of a trutle).

I read recently on a craigslist post of someone selling IBC aquaponic systems and they stated that pink tilapia are not illegal here, so i will be contacting that poster to see about obtaining some of those if I can. I am also looking into catfish and plecos. I think if I could find a few large plecos that need a new home, they would mow through the algae much faster than other creatures. What do you all think of that?

Can someone turn me on to a design for hanging planters off of the side of the pool?

I'm thinking to filter with an IBC tote that is plumbed into the bottom and filled with gravel, after an initial settling tank that I am still trying to design, then when it clogs, i can just backwash using gravity. Will that work? I know the guy Erik who made the swimming pool to pond conversion has his filter plumbed to push the water up, but he also started with clean water..

THanks for all the help guys!

This is great, I can't wait to see ho this progresses

Hey Nik:

You are on the right track. Good Job!

The water quality is good!  Time for fish!  Goldfish are very flashy as opposed to most fish who are trying not to be seen.  You will enjoy the goldfish for their visual effect.  I am happy with the many fancy tailed fish in the pond...

You are welcomed to create any kind of filter you want.  Bear in mind if you create an IBC tote filled with gravel you will have at least a ton of rock to move to the filter location.  After that you will have to move the rock into the IBC and then you will probably have to figure out how to remove the rock when you want to clean the filter.  Bare in mind you already have 35 gallons of muck that would have clogged your IBC and you would be well on your way to figuring out how to clean it.   That is why I suggest the removable lifetime filter media I use in my filters.  I saw a coconut coir pad the other day in the hydroponics store.  It had very similar features and would work well but may not holdup as long (years) as the cooler pad.

Here is a break down of the bucket filters I currently use at the raft bed.  I plan to change them over to the ones I described the other day (above). 

The water flows from the sump into the bucket. a tomato growing support keeps the filter from collapsing under the weight of the water and muck, it also keeps the media away from the sides of the bucket allowing the filter to flow 360 degrees maximizing the filtered area.  Water runs into the RB via 3 holes in the bucket.

Here is the filter media and bucket parts. You can see how nasty the media gets.  On the left is the outside of the filter which is relatively clean.  You can see in the lower left corner of the photo there is a notch in the media.  This where the inlet pipe comes into the bucket.  When the filter is clogged the muck gets that high and the water overflows there.  You don't need to clean the filter until that happens.  There are lots of good microbes in there too!  The grass along this sidewalk grows really well with the fish fertilizer that gets rinsed here.

To clean the media just rinse the media with the hose, this took less than a minute to go over this filter twice and it was done!  The best part about the filters I described above is that you can move them to whatever location you choose.  Right now they will work great at the side of the pool.  Later you can move them to the hill where they will filter the water before it enters the grow system, they are really versatile.  BTW I saw a system where the filter containers were large enough to hold a milk crate and they had filter media lining the 5 sides of the crate with blocks holding the crate off the bottom to allow the floor of the crate to become part of the filter increasing its efficiency.

this is the main filter for my system.  I posted the parts earlier in this discussion.  I used 4 layers of the same media.  As you can see the water is flowing through it in this photo as the pump is currently running.   The fish swam in there to clean things up for me while the water level was over the white grate that holds the filter in place and are trapped because they didn't leave soon enough after the pump started, doesn't seem to bother them much.

Many folks here are not sure I have enough aeration because I don't use filter stones, air pumps and the like.  There are 5 drops about this size in 10-15 feet this seems to be plenty of DO.  

Here is one last shot to show the water clarity.  Sheldon the turtle really enjoys hanging out on his rock. The fish cruise around it like kids in hot rods on Saturday night!

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