Backyard Aquaponics
A place to discuss aquaponics

We have recently in Hawaii and now Thailand started raising talapia in an aquaponic environment.

I have visited a few commercial ventures and we are currently in the R & D phase, and just getting ready to expand into commercial production.

One of the things I noticed about the systems I visited was they did not use there fish tanks as hydroponic growing areas. When I asked about the reason I was told that the fish eat the plant roots. It would seem like you could enclose the root system of the plants in a screen to protect them from the fish and save on needing as many supporting vegatable beds.

Has anyone tried this type of system.

Would the floating trays be enough of a biofilter to deal with the Nitrites in tanks with a high volume of fish or would additional beds be nessasary.

Does anyone know the appox. sq footage of vegetable bed needed per lb of fish in production.

Thanks

1 sq ft of gb = 1cb ft of gb = 27 litres.
So 1 sq ft of gb per 27 litres of fish tank. Minimum. Using 1:1 ratio.
We say 1 kg of fish per 20 litres I think (check this value)
so 1.5 kg or 3lb of fish per sq ft. If my quick calcs are correct.

Nope ... we say 3kg/100L... or 30kg/1000L...

With sufficient filtration and aeration.... people can maybe push that to 60kg/1000L.... especially with such a forgiving fish as Tilapia...

UVI (University of the Virgin Islands) uses about 57 grams of fish food per square meter of growing area per day. Using an estimated FCR (feed conversion ratio) of 1,8 for tilapia, that would mean an average daily fish harvest of about 32 grams of fish per square meter of growing area, or about 11,5kgs of fish a year.

That's about 2,4 pounds of harvested fish per square foot of growing area per year.



I believe I once saw a picture of a commercial system with a single fish tank over the entire area of a greenhouse, with floating rafts with lettuce over a big part of it. I can't find it right now, though, but I think it should be possible to do it in the way you describe.

Floating rafts alone is not enough though, especially in a big commercial operation. You don't necessarily need plants in growbeds filled with media, but you need at least some form of filter system for solids filtration and some place the bacteria can break down ammonia into nitrite, and then into nitrate.

ok so a little under 2 lbs per sq ft. Sorry.

Thanks for your quick replys.

We have a green tank in Hawaii for breeding 3000 gallons for 50 breeder.

We got started by being offer talapia out of a pond that was leaking. We transfered about 600 talapia into two tanks 150gal and a 300 gal tank fish sizes from 1 to 4 inches. We mounted a small biofilter above the tank. (about 5 gal of media, gravel). Didn't have any problems at this point. Then we started floating rafte with plants, just for fun more than anything. They were doing well at first but than we noticed the roots were being eaten.

We visited friendly aquaponics on the Big Island of Hawaii. Nice setup.

What I have set up in Thailand now and getting ready to start up is a 900 liter tank with floating beds cover 90 percent of the surface area appox 3' by 5' by 4' deep. I want to add a gravel ebb and flow bed to the system for growing crops that require more support such as lettuce. I think I'll put a biofilter between the fish tank and this bed.

From what I can tell I will need a biofilter at some point so I might as well get the benefit of the additional beds.

Friendlly aquaponics were running amazingly large number of fish in very small tanks and not using much of a biofilter, if you can call what they had a biofilter at all.

They had 6 tanks 4x4 with varying sizes of fish in each tank. up to around 200 1lb fish in the last tank. There filtration was 2 small chambers about 2' x 2' x 4' deep for settling out the solids and a 1x1x4 feet deep chamber filled with a plasitc netting and then out into 2 4'x 20' floatation bed with lettuce. Pretty cool set up. They were blasting the 6 tanks with a lot of air. I will post some pictures when we get opperational . Probably within the next few days. Plans were to set up tomorrow and have the fish delivered on wednesday but that could get pushed back a few days. Fish here about about .03 usd each for about 1in sizes. Not even sure it going to be worth hatching my own at those prices. Well thanks again one and all. I'll be around. Glad that I found this site as it will nice to have people to bounce Idea's off of and get new ones. Rken

Two key... critical points about the Friendlies system...

Solids removal... and mucho, mucho air.....

Oh and Tilapia...

The waste solid removal is accomplished in the first of the tanks 2x2. It is v shaped at the bottom with a simple valve at the base. The solids settle in this tank and are removed via the valve at the bottom. The beds I would Imagine need to be cleaned on occasion. But all in all a very good systems. I'm just trying to eliminate the pumps. I will give it a try without the biofilter and gravel beds to start with and see how thing proceed. I might have enough surface area with the floating beds and screen separators between the fish and the plants to keep up a good water quality. I will be keeping a close eye on the water quality at start up and for a couple of weeks into the project. Things are so cheap here in Thailand. I only have about 350usd invested so far.

600 liter tank

air pump .80L3/minute

Food for 6months

floats, pots, seed and fish etc..

Rken, please do not take this personally... I'm merely trying to prevent a disaster...

In my previous post regarding the "Friendlies" operation I pointed out two "key" points....

Solids removal and mucho, mucho air....

The "Friendlies" operation is an adaption of the UVI model of aquaponics, a model that evolved from considerable knowledge of RAS aquaculture techniques related to bio-filtration and oxygen demand requirements... and adaptions of techniques to acheive these...

Not the least of which is the lowering of BOD - biological oxygen demand..... and bio-filtration... by the almost complete removal of solids..

I can not understate the requirement for bio-filtration and oxygenation .... in any style of RAS aquaculture or aquaponics...

The UVI model utilises their raft beds to provide the remaining requirement for bio-filtration....

But only succeeds by the prior removal of solids and injection of considerable oxygenation...

The Friendlies operation has modified some of these processes and have to date had reasonable success... but they are... IMO... still a new operation and as such somewhat unproven...

Both systems involve considerable water exchange regimes...

IMO.. and it has been stated by others here on the forum who have tried merely floating rafts on their fish tank.... your results will be dismal at best... and catastrophic at worst...

Your floating rafts just will not be capable of providing sufficient bio-filtration on their own... the roots will most likely clog, and your plants develope root rot... or be nibbled by the fish, especially Tilapia...

Sorry, but I think you need to develope a greater understanding of free standing RAS aquaculture systems, filtration and oxygenation requirements.... and a greater understanding of how such things are not only inter-related within a UVI style model... but the utmost importance of those relationsships...

The need for bio-filtration... and/or solids removal... is paramount... full stop...

That's why the models of the UVI systems... and flood and drain aquaponics have been developed and implemented... because they work... and many failed experiments have proven that other approachs dont... or have limited success..

As I understand it, both systems use solids removal, but also get a lot (or all) of required biofiltration from suspended clumps of bacteria and (possibly) from bacteria growing on roots. As noted, lots of air is essential to this sort of thing working, but I am not sure if it is more for the O2 requirements of the roots (so they don't rot) or for meeting the O2 demand of decaying material or what.

Hi RupertofOZ

Thanks for the information. I visited the friendly farm. Quite a setup. The solid removal was accomplish in a settle tank on there system and there bed were the biofilter. seemed to working quite well. I appreciate your concerns and will take them under advisement. I have 3 tanks running in Hawaii at present. 150gal, 300gal and a 3000gal breeding tank. The smaller tanks are not connected to beds as of yet but are just using biofilters. I have a biofilter system ready to go for the tank I spoke about in my above post should things not work out quite the way I hoped and am thinking of adding a ebb and flow bed if needed if the one tank can support more garden space. start up should be next week so I will keep you informed of my success or failure. Just waiting for the plants to get to a place where they are big enough to do the job. Also I have developed a way to keep the roots protected from the talapia. Only question I have is if my bed will be big enough to act as a sufficient biofilter. Based on the number of fish ratio to raft bed at friendly I should have enough. The tank I am using has a slope to one end with a value for draining solids. If this should prove insufficient there is always the vacum method in a pinch until other measures can be instituted. By water exchange are you referring to draining a percentage of water out and adding fresh water. Friendly said that they did not do this. I agree that a lot of air will be required. Do you think the air pump I have is insufficient. The tanks I have in Hawaii only have small fish tank bubblers ($12 dollar types) and seem to be working just fine. No dieing fish and with hardy appetites. I see removal of solids as the main problem with the design of my current system.. I have extensive experience in hydroponics but am just getting into the fish side of the equation. I have grown lettuce which is going to be my first vegatable I grow. I have grown lettuce in standing water. No air no circulation with no problems. Other plants do not do so well. Basil also does well in this type of enviroment. Your comments and concerns are appreciated. I look forward to your comments after my reply. I do not want to project that I'm a know it all. Just getting my feet wet and any advise is appreciated. Thanks rken

which island are you on?

I'm on the Big Island 1/2 the year and in Thailand the other half of the year. Currently in Thailand. I just got back here about 2 weeks ago so I will be here for about another 5 months. Are you in Hawaii. rken

Critical process for efficient fish culture

Lots of Oxygen.
Solids Removal.
High Specific Surface Area for nitrification bacteria
Stable Water quality.

The more air you add, the more efficient your Nitrification process.

The more surface area you have i.e biofilter, plant roots, tank walls, fish net, etc the more space for microbes to survive.

The stability of water quaility is paramount, if the water is no good, the fish will be no good - plain and simple.

UVI system basic ratio at approx 50kg/m3 of Tilapia stocking density is 1 m2 FT surface Area to 8m2 GB surface Area. Very ballpark estimate, however it really come down to protein content/ NH3 concentration in water.

rken,
It will be interesting to hear about your results, please do your experimenting carefully though as I don't want to hear about huge numbers of stinking dead fish.

I think part of the reason most people don't do the floating rafts directly over the fish tanks is probably just logistics, How do you harvest fish from the tank when your crop of plants is in the way? It is probably easier not to have to worry about lifting plants and keeping them alive while trying to net the fish. Also, having separate beds with additional water in the system for the plants provides a huge amount of additional buffer for the system. The more water in the system above and beyond the fish tank capacity, the more stable the system and water quality will be.

Having the surface of the fish tank open to air provides extra aeration all on it's own while if it is all covered over, you need more active aeration.

Please tell us how you go with this idea. Points of special interest will be;
*Aeration, how much air you need per whatever unit
*Solids, do solids build up on the root protection cages or on the roots? How are you removing solids?
*Bio-filtration or how much fish can survive in some size tank with only the tank walls and raft/roots for the bacteria

Also,
Feeding if the tank surface is covered by raft and plants, how do you go about feeding and making sure you are feeding the right amount. How much feed is getting lodged into the root protection baskets before getting eaten? How much feed gets splashed up onto the rafts to rot and smell up the place.
Seeing the fish. If the surface of the fish tank is covered by rafts, how to you see and inspect the fish? I don't like having fish in a tank where it is really difficult for me to see them. And if it is covered by rafts, you might not even see a dead fish after it floats up, it could be lodged under the raft somewhere unseen to cause really major water quality problems.

Good luck with it, let us know how these things all sort out.