Aquaponic Gardening

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 I have had my system going since March. the first one was  a 30 gallon tank and then I enlarged it to about 100 gallons. I thought my system had cycled with 15 fan tailed gold fish so I added 25 catfish 3 weeks ago. Three died the first day and they have continued to die off,  so I am now down to 8 fish. The gold fish I cycled with were doing well I had 15 of them and only one died over that 3 month period after I added catfish(4-6) inches they either ate the fish ( they did not like the fish pellets or would run them into the pump and then eat on them. I lost several catfish due to them swimming into the pump or a couple of bricks that were in there because the larger fish would get stuck. I obviously moved the bricks once I found them, but that was 3 at one time. I think I my have to go to hydroponics because I have always been able to grow plants. I have had large gardens and they do well, but apparently I am failing at the fish apart which is at the heart of this matter. The water usually test PH 7.2 ammonia 0-.25 Nitrites, usually O, Nitrates about 10. Now I do not have enough fish to even keep the system going.  Today the water test was: ph 7.2, ammonia 0 nitrites 0, and nitrates is less than 5. One other thing after I had already lost several catfish for no apparent cause the pump quit working at full capacity, while I was at work and the water spiked.  1 nitrates and ammonia was around 1 also. I did  almost one half water change with rain water,  then and switched pumps. I had tested daily since I put the catfish in, at least until this past week because I am frustrated.  I did not see any sign of disease.

Thanks any input would be appreciated.


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What color is your fish tank?  My catfish died in a black tank due to temp spikes in the day.  While several people grow catfish here in recirculating systems, I have always found them to be one of the trickier family to play with.  Which is funny, because I can grow the heck out of them in ponds with less control.


My tank is black.  What type of fish do you grow? I live in Missouri and I thought that catfish would be the easiest fish to grow, especially for this climate.

Having a system cycled up with 15 goldfish does not mean you will not have spikes when you add 25 more fish.


Now having a fish go get wedged somewhere and die or munched by a pump and die means you probably had some ammonia spiking going on after those incidents and an ammonia spike is something that will certainly weaken catfish.  In addition, a 100 gallon tank is not a big tank and if its out in the sun you may be having some kinda extreme temperature swings which will reduce the available dissolved oxygen in the water and reduced dissolved oxygen levels are also a quick way to weaken catfish.  If your water temp is getting over 86 F I definitely advise supplemental aeration and if the water temp is not dropping below about 78 F consistently at night that aeration becomes even more important.


Now what makes you say you don't have enough fish now to run it as aquaponics?  If you have any, I mean any, nitrate reading, you have enough fish for your plant load.  I would only say you are lacking for fish if you have 0 nitrate reading AND your plants are showing signs of nitrogen deficiency.  There are many aquaponic systems out there running with 0 nitrate readings but as long as the plants are growing well, there is no need to have more nitrate that that.  Your plants are all looking very green to me so nothing tell me you don't have enough fish.  12 fish in a 100 gallon tank seems quite appropriate to me but only if they are small kinds of fish, channel catfish get too big for a 100 gallon tank in my experience and I've never managed to keep them healthy past the small fingerling quarantine size in a 100 gallon tank.  I do far better with them in 300+ gallon tanks.  Also, 300 gallon tanks provide far more temperature stability than a 100 gallon tank system will.


Another thing to look at for unexplained fish deaths is the fish feed.  I lately had a problem with fish dieing or getting sick and it has all cleared up since I got rid of some very old feed.  Fish feed has a limited shelf life and the higher the protein the quicker you need to use it up or it will spoil.  Using spoiled feed can really do you in for water quality and fish health.  Also, cheap feed can leave you with problems too.


So I would recommend getting your pump into a basket appropriate to protect the fish from it but hopefully not clog too quickly requiring you to clean it too often and then see how you go from there.

I grew channels and hybrid catfish from Auburn University.  If possible, stick a max/min thermometer in the tank and see how bad it gets.  Anything 30 degrees Celsius and up is not going to go well for those fish. 


Also as temp goes up, the max DO, or saturation point, for that water goes down.  You have to make sure it stays 3mg/l or higher.



I agree with TClynx.  A fish part being stuck in the pump might also explain the reduction in capacity.

I replaced the pump immediately- I had a spare pump in case something like that happened. I took it apart it just had some fish food and a beetle or two in it. I think it was just made cheap; it was made in china. The temperature spike were probably the cause of most of the deaths; the water was warm on some days.

I've had channel catfish easily handle water temperatures over 30 C or 86 F but at that point feed needs to be reduced a bit and supplemental aeration becomes important.  My daytime water temps in the big system have regularly gotten up to 32 C (89 F) this summer and in previous years when the system was different I think I probably had highs of 34 C or 93 F in the catfish tank but I was supplementing with lots of air and my flow rate through the tank was on the order of 3 or more times the tank volume per hour.


All my systems have supplemental aeration (when I tried going without, I found the fish went off their feed when the water temps got up to 30 C)  and I also pump a lot of water for my systems and circulating twice the tank volume through my fish tank per hour I feel is kinda a minimum when growing large numbers of fish in a tank (1 small fish per 5 gallons or 1 big fish (catfish are big fish and can be treated as such as soon as they are big enough to eat the grow out food) per ten gallons is a large number of fish and worth the extra flow rates and aeration.) 


But you don't need many fish.  Rob's whole greenhouse system runs on a relatively small number of goldfish and my 300 gallon system has been running a nitrate level of 5 ppm for months and I think it's great actually.  So don't let info like you need 20 lb of fish to provide for x square footage of plants sway you, those type of numbers are for systems where they are removing most of the nutrients from the water in the form of solids before they even send it to the bio-filters.  Take a deep breath and let your plants, system and fish tell you where things stand now.  Monitor water temps and see if that is the big problem, if so there are ways to perhaps mitigate that a bit.


If fish are still dieing, come back and we can see what might be done to help them survive.

I have extra aeration; it is supposed to cover 180 gallon. I have had that running since I first started because I had read that the extra oxygen would help the plants grow faster and it was good for the fish, especially if the ammonia or nitrates  ever spiked. The water cycles about every 30 minutes- flood and drain with a bell siphon. I was actually aiming for at least 10ppm for nitrates so I could grow tomatoes.

This small system is an experiment. I plan to install a green house in the near future and I  decided to try aquaponics, otherwise I planned on growing things hydroponically. I used to have a garden that was 3/4 of a acre. and it always did well but there is a lot of water wasted so I started reading about aqua & hydroponics. I have a 300 gallon tank, at our ranch, but I am in the city now and  going to school, so I did not want to make this very big. I just wanted to experiment. My husband and I have a large ranch and it would not be a problem to put the tank under trees  or  have a shade it in the shade and pipe the water from farther away: however I want to make sure this is what I want to do. This fall I plan to install a small hydro system and see what type of results I get.

Thanks for your help,


Aquaponics can do very well but it does require a bit more patience in the beginning.


Track your water temps because if you switch over to hydro, warm nutrient can actually cause you even more trouble.


You do not need a particular minimum nitrate reading to grow tomatoes.  You might just need to dose a bit of seaweed extract to get enough potassium to get the tomatoes flowering and fruiting once the system has stabilized.  Unlike hydroponics in Aquaponics potassium is more commonly the limiting nutrient since fish feed generally provides more than enough nitrogen and phosphorus.  Once things are ticking along nicely you may find that your nitrates fall to 0 and your plants start showing signs of the lack, in that case you might add more fish or perhaps feed a higher protein quality feed and that may take care of it, otherwise you may find you need more filtration.  I like to have twice as much grow bed as I have fish tank.

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