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Hi all,

My name is Steve and I decided to start aquaponics. I have been researching for some time and decided to try it all and see what works best.

I would like to do projects with my NGO and support the community by giving job opportunities for the disabled. My project will be focused on simplicity, recycling and use of natural resources.

But before I start with the project I want to try it in my backyard and get some hands on experience.

I will start with 2 separate CHOP systems based on a 1000lit fish tank each. Each fish tank will have corresponding 4sqm of grow space to comply with the 1/1 ratio. One system will contain a media grow bed + DWC bed. The other will have a wicking bed + DWC. Once I have it set up I will later add vertical towers (using recycled plastic bottles).

The way I envisioned it is the water to free fall from the fish tank to the media bed (or wicking bed in system no2) and from there to the DWC, and finally the sump tank. At first, the water would be returned from the sump to the fish tank by a single pump. Later, I would divert the water from the sump to the towers. From the towers it would drain into a single NFT pipe that drains back into the fish tank.

I would use the DWC for leafy greens only, the wicking bed for rooted vegetables, the towers and media bed for peppers, tomatoes, strawberries etc.

As for the fish, I don't have much options. It will probably be carp. Later on when I have more confidence in the system, I might try trout but will have to find a way to cool down the water.

Now, my questions.

What size sump tank would I need?

How to calculate the fish tank/grow bed ratio once I add the towers? (my idea was to calculate the number of plants in the grow beds and add at least that number in the towers. I would not go beyond a 1/3 ratio)

Would I need a swirl or some other filter between the sump and towers?

If yes, can the sump be modified as a bio filter?


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Zdravo Stavane,

You don't need to "comply with the 1/1 ratio" even in the set and setting that that "rule" was conceived in (sump-less media bed system) would not apply in your scenario, since you will be using a sum...and a DWC component. So you need not take that ratio into consideration...

0.0283 cubic meters of media can perform bio-filter duties for a MAXIMUM of about 450 grams of fish biomass...but plan for less fish bio-mass than that to avoid unnecessary headaches 300 grams is PLENTY per 0.0283 cubic meters of media (also your choice of media and it's SSA [Specific Surface Area] will affect this. The above assumes that you'll be using some sort of LECA material...

For your plants to do well in your DWC component (assuming a 20cm on centers hole spacing for your lettuce rafts) you would need about 130 to 150 grams of fish for every 1 square meter of DWC surface area (assuming a water depth of 20 to 30cm in the DWC trough)...

I wouldn't suggest going from wicking bed to DWC...but try it and please let us all know what you find :) It would probably work much better to "dead end" the wicking bed after the DWC.

Your sump tank size is determined by your media bed volume. and how much water it takes to fill that media bed up. Most common media (rocks, LECA and such) will displace about 40% of the water it takes to fill that same media bed id it was devoid of media (Archimedes). Then you must take into account that if your pump is sitting in the sump tank, you need to always have around 10cm (or so) of water depth above the top of the keep the pump from potentially sucking air, becoming damaged and failing on you.

A good strategy may be to plan for (as massive as possible) bio filtration capacity through your media bed(s) and treat everything else (towers, NFT etc...) as "add-ons".

If you run what is called a clean water sump (their are also dirty water sumps), and you keep your fish mass on the low likely not need a swirl filter before the towers and NFT...if you get creative with the media inside your towers, they can act as mechanical as well as biological filters...but honestly, I'd forget about using recycled plastic bottles as towers will be "fun and cool and hip" for the first couple months, but will likely quickly become a major pain in the ass to actually maintain for any length of time. (Of course, don't let that statement keep you from trying it out for yourself if that is something that you want to do).

Yes the sump can be modified to do some bio-filtration duty...

Also, be aware that you can use the DWC as a sump (I personally don't like that set-up, but know people who have done it).

Pozdrav i svaka sreca!

Pozdrav Vlad,

Thanks for the answer, you cleared up some issues I had.

I didn't realise the 1/1 rule applied only for media beds.

As for the fish, I planned on trying 15kg. that would be about 300g of fish per 20l of FT water. However, if I use my 2sq meters of media bed as a filter, using your calculations that would mean I could have about 9.54kg of fish total. Having in mind that I will eventually have the towers that will also perform filtration, the 15kg I started with do not seem drastic. Especially if I make an additional bio filter out of the sump.

Why do the bottles require so much maintenance? I read people use swirl or other filters prior to the towers to avoid solids building up in them, reducing the need to clean them (providing I spray paint them to reduce algae growth).

Yes, the 1 to 1 ratio applies to media beds WITHOUT using a sump.
You should never stock a system according to the fish tank water volume capacity, but rather to your bio filtration capacity. But truth be told, even that is not entirely correct. Often in aquaponics we need more mechanical filtration than bio filtration :)
Yes, of course we can take care of that with various types of mechanical filters (swirl filters, baffling tanks, net filters etc...) But why would you pay good money for a plant food input (fish food) only to then filter it out and remove said input from the system? That would just amount to a really expensive way to grow some plants... ;)
It doesn't take that many fish to grow some lettuce/ leafy greens. If an NGO is footing the bill for such a project, then sure, I guess it probably doesn't matter. But in a self sustaining profitable venture, you probably don't want to be using more inputs than you need to, and you most certainly don't want to be removing said inputs. (Unless you were selling them off, or they were part of a larger fertilizing scheme for another part of your using the waste from the swirl filter to fertilize a garden which saves you from having to purchase inputs for that part of your operation). Quality fish food in Serbia is expensive. And it is much cheaper for people to purchase carp (tovne, masne ribe) from one of the many fish farms. One kilo of carp costs...what 350-400 dinars and take you a year or two to grow out (and feed) opposed to getting150-200 dinars for a head of QUALITY lettuce that takes about 6-8 weeks to grow?

The NGO will just provide a start. My future project must be sustainable as it will facilitate the employment of disabled young adults (for example people with Down syndrome) that cannot find employment. It is a very complicated problem that is not really for this forum so I won't get into details.

But it is very important that this future farm is self sustaining and able to provide multiple job opportunities. I envisioned to develop a steady customer base that would buy the products on a regular basis, maybe even organize delivery straight to their homes.

But, my plan is even more complex. I actually recently won a grant from the Rocafeller fund to start my red worm farm. I started thinking of making a fish farm (as I will have about 3 milion extra worms each month) and that's how I found out about aquaponics. So, in a sense, the aquaponics production will be a continuation of the red worm project. Worms will provide nutrients for the fish (I just have to check if a steady diet of red worms is sufficient or would I need to add suplementation).

As for the fish, you are correct. My main goal would be to maybe raise enough carp to sell to family and friends for Christmas :) The main profit would of course come from the plants. However trout is highly valued here, and once I am comfortable that I can maintain a healthy and cool environment, I will try to raise trout.

My brother actually runs a traditional vegetable farm with a couple of grennhouses and I would love this to be a step towards going full organic. So reusing waste is not an issue :)

But before I even start writing a project, I want to test the system for some time and see what works best for us. I hope I can get it up and running this fall at the latest.

Hi Stevan,

I've found trout to be easier to raise than some people suggest.  As long as you supply enough oxygen they're pretty tolerant.  Is there a reason you're shying away from a dedicated biofilter, such as a moving bed media filter?  They don't cost much to make.

Hi Jeremiah, not sure what you mean by a moving bed media filter? I am not shying away from any option, just want to keep it as simple as possible. From what I've heard the media grow bed serves as a biofilter quite well..

What is a moving bed media filter?

It's basically a bucket that the water flows through that's filled with these with an air stone in the bottom.  It will do your nitrification for you (i.e. no media in your grow bed needed) if you have one of them, though, you would need a solids removal filter (like a swirl filter or a media bed) first.  It would allow you to raise more fish without worrying about too much ammonia.

I've got a set of plans on my site if you want to see how it works.  If you scroll down you'll see they're free for a little while.

If you ask me, media beds without solids removal filters are a hassle long term.

That basically looks what's called a fluidized bed filter (in the aquaculture industry) aquaponics (hybrid designs) it seems like folks 'usually' have enough bio filtration, but not enough solids filtration ( like Jeremiah already alluded to)...

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