Backyard Aquaponics
A place to discuss aquaponics

A quote of Journeyman in this post:
viewtopic.php?f=12&t=16031#p383988
where he says:
"Another advantage is in small areas - not everyone has a large area for multiple GB's so adding in filtration can increase how many fish they can have without impacting too much on space".

This is exactly why I want to place a vortex filter in my aquaponics system.

*** Can anyone tell me what are the ideal ratios in an aquaponics system without a vortex filter?
(Tilapia)
Stocking density: 25Kg/m3
Feed rate: 2% = (Max. feed / day: 500 gram)
Feed rate ratio: 500 gram / 20 gram/m2 = 25 m2 growbed.
(This are ratio's. I do not have 25 m2 of growbed!)

*** And what are the ideal ratios with a vortex filter?

Thanks,

Hi Vin, welcome to the forum

Seems like you've already posted some stocking densities (I'm not sure where they came from or whether they're correct) for the before vortex scenario. I don't know that anyone here will be able to tell you the other information, that parts going to vary with your flow rates and how well you design the filter. I think that most of the people who are using additional filtration here, use a Radial Flow Filter which appears to work slightly better than a swirl filter. These types of filters do not remove suspended solids so you still have nutrients flowing through the system but the removal of the settleable solids reduces the amount of nutrients the system needs to handle and lets you grow more fish. If your focus is mainly on growing fish, there are some people here who have Recirculating Aquaculture Systems (RAS) and you may want to check those out. You can still use the nutrients for plants but they are designed with enough filtration that they don't necessarily need the grow beds.

Is your system inside or are you planning on heating the water?

Cheers

I am designing my aquaponics system as a part of a self supporting sytem.
This system will provide me drinking water, energy and food, and it will recycle my waste and wastewater.
I am planning to make a small unit with the same ratios before I start building on a large scale.
Ratios and numbers are very important to me because everything is depending on something other. By removing solids I can remove nutrients from the system if I need to. So this will give me the opportunity to scale the ratios and let all parts fit together.

This can for example be important in the winter. Yes I will heat the water 25°C (77°F) but I am not sure if the plants in the growbed will remove nutrients effective due to a shorter daylength.
And it gives me the opportunity to adjust my production to demand for a certain period.

If there is anybody that can give me advise on these ratios... I will base my ratios on feed introduced into the system.
I read about feed rate ratios of 60 to 100 grams per m2 of DWC. Is that possible because solids are removed?
And if I remove solids can I handle a feed rate ratio of 60 to 100 grams per m2 of growbed? (Instead of 20 grams / m2)

I will go reading about RAS.

Hi Vin,

When you say you want this to recycle your waste I'm not clear on what you mean - I know in greenwater systems in Asia they sometimes use human fecal material to fertilize ponds where they grow fish. I doubt this is what you meant but just in case, we generally advise people not to allow the manure of warm blooded animals into their AP system for disease reasons.

Looks like the feed ratios that you posted are from the University of the Virgin Islands raft model. I believe the media bed numbers I have, came from Timmons and Ebeling but I'm not certain, they would be 25% of the UVI rate so 25% of 60 - 100 gms/ m2. Someone with Timmons and Ebeling's book might set us straight as to the meaning of their media bed numbers.



Yes, you absolutely have to remove solids (some pass through anyway, even with the best efforts at removal) with a raft system like at UVI or you get solids coating the roots and causing problems. There's more than one way to achieve the higher feed ratio - you can feed more to the fish you have or you can get more fish and feed the same or less food to each. UVI has four fish tanks so achieving the 100 gms fish feed/m2 isn't really as much of a challenge as it may seem. As far as the fish are concerned you can grow more if you remove solids from the system because those solids release compounds on breakdown that use up part of your filtration capacity. By removing them you gain some production capacity because your bio-filter can still break down all the bad things that would affect the fish. Since most of the breakdown is done by bacteria in the grow beds, rafts or bio-filter, it's really more dependent on them than on the plants, how many additional fish the system will allow if you remove some of the solids.

Hope this makes sense to you.

My aquaponicssystem will be a closed loop, except for the fish food wich will come from outside my aquaponicssytem. (Duckweed from my wastewater treatment system, worms from composting etc.)



Yes that's right.



Yes I understand. I prefer a media filled growbed. And I want to use NFT (Instead of DWC) to save space. I can put NFT against the wall. If I (In time) want to make use of a DWC, then I will use a part of my growbeds for this purpose. (So I have in mind.) In that case other growbeds can remove the solids.



Of course... Nitrate is little toxic to fish. That will solve my problem for shorter day lengths. Thanks, I forgot.

Nevertheless, I still remain left with the same question. I will breed my own fingerlings. I am planning to make a small unit with the same ratios before I start building on a large scale. I think it is a waste to breed lots of fry and only stock 15 fishes per pond.



Yes, thank you

This might help get you in the rough vicinity



The info probably came from the Earthan Group originally.

1.56 lbs = 0,45359237 Kg fish
1 ft3 = 28,3168466 Liter wet gravel

That's the same as:
0,71 Kg fish / 40 L wet gravel / 20 L water (Assuming that 1 L of gravel can keep half of the volume with water.)

That is the same as:
50 Kg fish / 1/1,5 m3 fish pond / 2 m3 wet gravel / 6,66m2 x 0,3m growbed
Growbed (water) depth = 30 cm = 300 L wet gravel and 150 L water per m2
2000 L / 300L = 6,66 m2 growbed
Water exchange of 1 - 1.5X per hour:
6,66 m2 x 0,3 m deep = (1,998) = 2m3 / 2 = 1m3 water/hr to 1,5m3 / hr water exchange

Feed rate 2% = 1 Kg fish food / day
1000g / 20g/m2 = 50m2 growbed 50m2 / 6,66m2 = 7,5x

That's almost the same as the values and ratios I've held. Only you say that it is possible to increase the stocking density with a maximum of 7.5 times!
And that is very close to the values that I have found regarding the UVI system.

Thanks,

You totally lost me on this and some of the numbers don't look right when you go into the statement comparisons for example;

1000L = 1 cubic meter

2000L/40L = 50 .. so to say this;



.71 x 50 should = 50 Kg for these statements to be correct but it doesn't. I think maybe I misunderstood what you were trying to say though, anyway a bit tough to follow

Anyway assuming the calculations get done right you should be able to get the answer.

The void space in the rocks varies but I think it's usually around 40%. This you can figure with a bucket if you want. It's been awhile since I've done one of these calculations so I'm not sure you even need it. Maybe someone else who's done this more recently will chime in or I can find it looking back through the threads.

There's some additional information that you might want regarding fish stocking but I don't know if it will be useful to you (seems like what we already have is what you're after - here it is anyway though) - http://www.backyardaquaponics.com/forum/viewtopic.php?f=12&t=6646

Hope this helps.