Aquaponic Gardening

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Hello Aquaponic World,

I hope someone might take a moment and remind me why I'm doing this....

I have now had plants growing since last October in the the AP system and the volunteers growing in the yard are doing better than my AP plants. I am about 25 fish away from going Hydroponic... Here's why.

Last October I built the system.  Since then I have had 35-40 large (4-8") goldfish in the system.  Not a single dead fish.  Not much growth.   

250 Gal IBC (Fish tank)

4'x16'x10" gravel grow bed

4'x8'x8" DWC

60 +/- sump

32- 4 gal Dutch buckets

Water from well ph 6   correction PH is 7

System water  ammonia, nitrates, nitrites, 0.0  & PH sits around 8.0

Lots of aquatic snails

8-10 baby goldfish now 2" :)

Growth has always been super slow.  

Kale and mint doing great.

Lettuce/spinach/ bitter and slow growing.

health lettuce started in grow cubes declines in DWC

Conclusion was not enough waste (nutrition) in system.  
Bought 100 Channel Cat and replaced goldfish with cats.  

Day one hour one 15 dead

Day 2 15 more dead

on day 7 now.  Down to less than 35 fish.  

Next purchase at this point is going to be a sack of fertilizer and some beer batter to cook the last fish and give up on the AQUAPONICs.

I had no idea there would be so much information out there yet no one able to help.  Been to every greenhouse "Garden" Supplier around.  Even went to the local bait and tackle shop to talk fish yesterday.  

I would love some assistance.

Thanks guys

I have pictures of my system and plants on my page.


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Mineralization tanks which are fed by the filtration system will handle fish waste breakdown. About 110 pounds of fish when system is fully running. It's calculated by fish feed rate per grow area. If you haven't read Dr Wilson Lennards papers on aquaponics and media beds - it's worth a read. He includes a calculator for proper sizing of media beds.

that is an interesting calculator.  At the end of the day it seems to generate about 1# fish per cu  ft of grow bed.  With 15# fish in a 250 gal tank.  So my current system would need 104# of fish and at there rate 7 -250 gal ibcs.   that's confirmation of what I have experienced.  Fish tank is nearly 1:2 ratio.  WOW!!!!

The ROI on that would be astronomical too.  I have less than $1000 in my whole system. And my ROI will be like 2 years.

My AP pond system is well balanced at these rates.

Hello Steve,

Sorry for the delayed response, looks like we've at least got some good discussion going, minus the iAV's troll. 

The API test kit is indeed very reliable, as long as it's not over a year old, hasn't been stored in a really hot area, hasn't been stored in direct sunlight, etc.... all pretty standard storage recommendations. 

So, regarding your stocking density question, you appear to want a clear and concise recommendation as to what it should be for your system. Unfortunately, it isn't that simple. If you want a simple answer, just use the Rakocy Standard of  feeding between 60-100 g/day/sq. m of growing area. If you also use a standard feeding recommendation of 1-3 % of body weight per day you can use those numbers to determine the total number of fish your system can support / needs. What throws a wrench into that formula is the crop or crop(s) that you are growing. Obviously, all plants are going to have different nutritional requirements, so what you are cultivating plays a very big role. Furthermore, the protein concentration of the fish feed you are using directly determines the your Nitrogen production potential of your system. (That's why I asked you in my previous post) In order to make any sort of calculations that is a necessary bit of information. Another factor is solids removal. If you have solids filtrations integrated into your system (I am a strong advocate), then you can potentially be removing as much as 60% of your total Nitrogen, so it's something to consider.

Now about your catfish, I'm not sure how much experience you have with fish but I would have to strongly disagree with your statement about shock; "Shock doesn't seem to make much sense, and a spike of any type wouldn't make much sense either.". When fish die as a result of stress of shock it is almost never an immediate thing. The symptoms of stessing / shocking fish typically manifest themselves days and even weeks after the event. The timeline you described for your catfish dying sounds absolutely textbook for fish dying that were not properly acclimated. And you unfortunately killed the one catfish that survived :/ If you were ever planning on breeding, he would have been an excellent choice as he had already displayed incredible signs of resilience when all others died. That's a great genetic trait to pass on, but I digress. There are a few reasons that your catfish might have gotten stressed when you introduced them to your system, the pH of the transport water could have been significantly different. The pH scale is essentially a measurement of hydrogen+ ions vs hydroxide- ions and it is a logarithmic scale. That means the a pH of 8 is ten times more alkaline (higher hydroxide- concentration) than a pH of 7. A pH of 9 would be 100 times more alkaline than a pH of 7, Etc... So basically, that means what might seem like a nominal difference in pH can actually make quite a big difference. Now catfish are pretty hardy fish, they can thrive in quite a broad range of pH (6.5-9). What they and all other species of fish don't like is quick changes in pH. Another water factor that could have caused their demise would be temperature. If your system water was vastly different from the transport water temperature, that could have stressed them as well. EC is another factor that could have stressed them. EC, or Electrical Conductivity is a measurement of all the salts in the water. Not sure what hydroponic solutions you have added to the water but that could have increased your EC. In additional to all the preciously listed reasons, some slightly less crucial factors could potentially cause enough stress to kill your fish. The water turbidity could have caused it, being to rough when handling the fish could have caused it, or the shipping company could have been to rough during their transit. The bottom line is there are a number of factors that could cause the fish to die in the exact manner that you described. 

To sum it all up, it sounds like you have a grossly understocked system and you have nutrient lockout due to a pH issue. I am also very curious what the Alkalinity is in your system. That ultimately could be a underlying problem with pH. If my hypothesis is correct, increasing stocking density would solve both problems. Autotrophic bacteria, such as nitrifying bacteria, will reduce system alkalinity and release positively charged hydrogen ions into the water lowering pH. So give them more food and let your ecosystem manage itself. NO need for a solely hydroponic nutrient solution system(conventional). You absolutely can supplement your aquaponic system but I'll save that for another post after we fix your pH problem. 

Please ask me any questions that you have and I'll do my best to answer them for you.

One last thing, if you need some good information on catfish production, the SRAC fact sheets are a great place to start:

For some more aquaponic specific numbers I also would recommend Dr Wilson Lennards fact sheets (nice recommendation Eddie Beuerlein) :

The Grandfather of aquaponics, Dr. James Rakocy, also has some of my personal favorite aquaponic / recirculating aquaculture information. A great place to start is his book, "Aquaponics Q & A" :

And lastly Steve, I'll put up some of my pictures hopefully by the time you read this post so you can see my little hybrid research system.



StevedNETN said:

Hi Benjamin,

Thanks for the thoughtful reply.

I have an API test kit. Has shown to be reliable so far.    You mention fish biomass. I can't seem to get a straight answer on fish quantity.  Look at my page and you will see my system isn't small.  64 Cu Ft of media is bigger than nearly any system I have seen.  600 gal of water in system and 40 +/- goldfish 4-7" log isn't tiny, but seems to be nowhere near enough.  

The catfish died over more than a 2 week period.

15 were dead in the bag from the stocker.

15 or so the the next morning.  most of them jumped out and died.

then 3-5 per day for the next two weeks.

I killed the last one because I got tired of waiting for him to die.

All the while there were 18 goldfish in the system with them.  Not one of them died.

Shock doesn't seem to make much sense, and a spike of any type wouldn't make much sense either.

Feeding them Purina, it's the only product available near me.  (feed maybe 1 oz a day) not really aggressive eaters.  

Plant load:  I have 45- 3 gal dutch buckets planted and 4x16' grow bed with lettuce and spinach and mint and kale.

Can't find any supplements that seem cost effective.  

Have done compost tea.

I have worms in the system doing very well.  

Had aquatic snails very healthy and reproducing.  (they like to ride in the irrigation system)

I have tested my gravel, and it doesn't appear to be highly alkaline.  It might be slightly.  Hard to tell.  

The fact that the nitrification process isn't driving the ph down tells me I need more ammonia = (MORE FISH)  well more fish died.  

Plant growth is terrible, look at my pictures on my page.

Since removing fish and switching to fertilizer the production has gone insane.  

My Conclusion is for a system as large as mine I need more fish.  If the rule of thumb is 1# of fish per gallon of bed than I need 64 +/-# of fish.  that is probably 10x what I have had at any given time.  In order to do this I would need a substantially larger fish tank and I don't see the viability in this.

My second conclusion is (If you are a fish producer who wants to filter the water than this is a great way to do it..  If you want fresh produce, I have a family of 6... This isn't realistic.)

How large is your system?  What is your ratio of fish tank size to Grow bed & # of fish?



Easy buddy, this is a friendly forum. We can agree to disagree, no need for the language. And, "super genius" is a Wile E Coyote reference.

Apologies for the "troll" comment, perhaps you can change my outlook. I'm sure you can understand how it looks when you push converting ones system over to a different growing method and then offer the link to a different website containing information on said growing method. I mean, that is after all, why we come to this website. We seek advise from our experienced peers. But what doesn't make sense is how that would solve the problem that was being described by Steve; pH lockout, nutrient deficiency, fish dying, etc... If you could please elaborate on why and more importantly, how converting his system over would solve any of his described problems it would be greatly appreciated. 

I not here to step on anyones toes or to offend. Again, apologies for the "troll" comment. Simply trying to help a fellow aquaponics enthusiasts. 



MT Mind said:

First of all, not a troll, so go fuck yourself.

Second, "Super Genius?"  Nobody's buying that.




MT Mind said:

You might look into converting the gravel bed to iAVs; the filtration of the coarse sand beds is much more effective than gravel at capturing the fish waste and converting it to available nutrients.  This also means cleaner water and a higher stocking density, so you shouldn't need to add supplemental fertilizer.  Here's a good place to learn the details:

MT Mind:

So where is your system?

I can see you are sold out to it, so proof of concept time.   Sand is obviously a good medium for lots of reasons we will all acknowledge.  It has one of the highest surface areas of any medium.  There are also many reasons against using sand.  We all spend lots of time researching and studying and then much money and effort in building these systems.  I have one of the largest systems I have seen on this site, and at the end of the day no one is able to give me a solid reason why the catfish died and the goldfish didn't (Except the possibility that it was delayed shock from temp and ph) .  The issue isn't the system design or media.  The plant growth issue is a nutrient deficiency.  That is undeniable.  The solution here is more fish, which I am not willing or interested in having as many fish as would be needed to sustain the plants i desire to grow.  Not to mention the requirement to then keep them alive over the winter (N.E. Tenn winters are below freezing for weeks at a time).  At this point, Hydro is the best solution for me today.  I may attempt to develop an organic digester to get away from the synthetic fertilizers, however i'm in no hurry today.   

Thank you to the faithful who continue to work this, i love the concept, but for me it isn't practical today.

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