Hi, Sonja. I have experienced the same cycle with my fish the last couple months. I've gotten some advice from the aquaponic specialist from University of Ar. She recommended water changes and to not feed them. If you change water, she recommends 20%. She also recommended a product called Zeolite which filters out ammonia, heavy metals and other things that are detrimental to the fish. In my case, my new fish were too small and she said couldn't handle the nutrient load. I planted all my beds, did several water changes, quit feeding for a week, and tested the water several times a day to monitor and make smaller adjustments, keeping PH within .4 max variance.( this is very hard here because my water is 8.4 from the tap and I kept it at 7.4 thru this) I also purchased the zeolite in filter bags and attached it to the discharge tube into my sump tank, causing all water to run through it. I haven'tlost any fish the last 2 days and started feeding 3 days ago. I'm hopeful it's over for now. I sure hope so since I've lost about 425 fish in the last month. I know exactly how puzzled you are about this, and hope that this info may help you.
Hi Sonja, sorry to hear about your troubles.
@Cindi, in your scenario i.e fish not being able to handle the nutrient load, zeolite to sequester ammonia, and water changes was pretty good advice. Unfortunately, Sonja is having 'the opposite' set of circumstances. No showing of nitrates, no ammonia. So we'll have to help her figure something different out, that fits her scenario...or at least try to...
Flashing is just a sign that something is irritating them, hopefully the state lab can perhaps shed some light on the matter, You've probably already thought about 'the usual culprits'...galvanized metal...copper in contact with the water...leaky stray electrical voltage from a pump/equipment...etc...
As to running your system without fish, and not using humonia since you are selling produce, while not relying on typical hydroponic nutrients...sure, there are a number of ways to do that...safely so that you can one day plug your fish back in.
You'll need inputs that make economic sense and that you readily have access to.
Physiologically speaking, how plants grow is how plants grow. Weather soil, hydroponically, aquaponically, vemiponically, peeponically, worm-tea ponically or "what-ever-pre-fix-ponic" we come up with. Plants are not very picky as to how they get their ions
To keep your bio-filter going you will need an ammonia source to feed them with. This can come from many sources. The dead rotting carcasses of your dying fish would be one potential source. (Free, available ready for nutrient recycling).
If you have farm animals, making your own salt petre from their nitre beds would also be viable, though it may be more viable to purchase the salt petre, as this process takes a long time. Salt petre would give you nitrate, calcium and potassium. Salt petre does not rely on bacterial action to free up those elements and make them plant bio-available.
Sea water is a great source of magnesium, some potassium, and many trace elements.
If the 'yuck factor' of rotting fish is too much...you can purchase a manufactured and pre-packaged fish emulsion product like "Charlie Carp". Many Aussies use it in their winter to run systems fishlessly, growing veggies, until it warms up, and they re-stock the system with fish.
If you have a worm farm, hanging paint strainer bags of castings near an air stone works, but you will still need an ammonia source to keep you bacteria alive during this time.
Just think about the 13 plant essential elements that plants need to grow (and having some N in the form of NH/4 to keep your bacteria alive) and you'll be fine.
Linked is a page with some common substances and their NPK and other mineral values. Some may not be appropriate unless processed correctly (mammalian feces...rabbit droppings etc)...Most have, or would work just fine. Just don't "over do" it. Keep things somewhat balanced.
You can also run your system on fish food (provided you are using a good quality well formulated feed) without the fish. Worms and microbes with do the same job as the fish, only leaving more of those essential elements for your plants, since there would be no fish to sequester the nutrients (turning the food into fish muscle tissue and fish bio-mass) contained in the fish food
Hope some of this helps at least on the plant and bacteria side, and possible ways to run your system without fish. As to the mysterious fish deaths, there are too many variables for any of us to reliably diagnose from way out here in internet-land.
I hope that you and/or the lab can find the root cause of their deaths.
Did you get to find out what the problem was? I am keen to understand what happened.
Zero TAN & dead fish?
My wife is a nurse educator & midwife & I am an air force electronics/ medical (CT,MRI,Nuclear Med & Pathology) engineer. I am searching the blogs for stories such as yours so I can incorporate outcomes into my AP operations reference manual plus ensure that our AP Lab can measure or deal with such a problem.
I run 4x 1000L IBC, 2 inch SLO’s , then Swirl filters then a mineral/ bio filters of ceramic beads, Zeolite & spaghetti mats to 4x 600L sumps then a 12K Litre/hr sump pump.
I use Humic Acid, EM & Probiotics in the system to help keep the bacteria balance on the good side.
The scientists here in Thailand say that the biggest problems are Bacterial infections & low DO due to water temp of 26-28c. I am doing everything possible to get the Bio filtration working well so I can run a 10M Deep Water Raft as well as grow beds. There is Zeolite in all grow beds.
There are Red Claw & Giant Malaysian Prawns in the 4 interconnected sumps plus a few Tilapias that got sucked up the SLO in sump pump.
I run a 1% sea salt solution (100L hospital tank)on all new fish which are Tilapia, Barramundi, 7 Stripe Barb, Julian’s Golden Carp, Spotted Featherback & Snakehead fish. The system has been operational 6 months.
I use a seaweed extract from Finland with German Humic acid & 17 trace elements on the grow beds weekly. I am pretty sure that this mixture will keep your grow beds going & if you need more NPK, there are several Organic supply places on the net.
Look forward to your future posts & resolution.