Backyard Aquaponics
A place to discuss aquaponics

Please take the time to read of my recent catastrophic fish kill here http://www.backyardaquaponics.com/forum/viewtopic.php?f=18&t=4099&start=225

I'm seeking advice as to how to start again after a total fish kill of which I'm unsure of the cause.

PS: sorry about the extra thread, but my original thread wasnt gathering anybody's attention...

Just posted a reply on the other thread Ryan... reposted here (with edits)

Your deaths are probably related to the fish being oxygen stared, majorly stressed and severly weakend from the pump failure earlier in the week... probably the primary cause...

But....

Your suspicions about the food are probably spot on... would indictate that the pellets had been "wet" at some time... possibly even by urine from rodents...

Never use feed that shows obvious signs of mould, infections, rodent droppings etc...

As such... I don't think your growbeds will be contaminated...

I'd definitely dump ALL your system water... tank, sump.... and allow growbeds to drain...

Wipe out your tank/sump with a mild bleach solution.... rinse and allow to dry... rinse again and allow to dry...

Partially fill... and pump through the growbeds... allow them to drain to waste....

Then refill the system and turn it back on...

Add some seasol to keep the plants ticking over until you can get some more fish...

Dump the feed...all of it...


Fish... up your way... don't know if you could run trout, not even sure if you're allowed...

If you can get some late season "advanced" Silver Perch fingerlings... you should be able to over-winter them...

Or perhaps some Murray Cod... and/or Tandanus catfish (ring Naomi Fisheries)

Better luck next time Ryan. Maybe try an AC/DC battery back up air pump to be sure. Sorry for your losses.

hmmmm,

I wouldnt be blaming the food at this point.

I'd say that the pumping failure caused an ammonia spike (that you didnt measure at the time), followed by a nitrite spike, once the pump was started. A lack of DO would have exacerbated this problem, but adding salt the morning you noticed the pump had failed may have avoided the deaths.

I shouldnt think that the tanks would need to be cleaned out - it does not sound like a lingering toxin caused the deaths. If your worried do a water change, aerate the water, clean out the pump, and start it all back up again.

Seasol and humonia / other ammonia source until you can get fish.

Maybe a backup system too? I use 3 seperate pumps now, running from seperate power sources (inverter, house power, shed power), even if I have a pump failure, it is not catastrophic, like yours was, and many others have been.

Back on the bike

Thanks Faye - that "all alone feeling" is starting to dissipate

I'll definitely be investing in an air pump. I did have a really old one here that I tried using after the pump failure, but it pushed out bugger all air, and made a noise like a jackhammer so I turfed it.

If the feed has been mouldy for some time... then it may be bacteria infected... almost certainly it has begun to decompose...

Hence its nutritional value, particularly protein content... will be severly diminished...

As it has been fed for sometime... the fish may have been in a weakened state anyway... the pump failure and oxygen starvation just fatally stressed them...

Reason I suggest cleaning the tank... is possible pathogens from infected feed... and dead fish...

If you're going to restock with fingerlings immediately... as you suggest in your other thread...

Then you might as well start clean.... the fingerlings could be stressed/weakened by transport... lingering pathogens could just raise the stakes of problems...

And salt your tank when you restock as well...

Interesting points OBO.

I forgot to mention also that the fish all looked in good condition (apart from a minor case of death!), except they all were floating with their mouths wide open. Also, throughout this whole saga, I never once saw them gulping for air at the surface, like the previous power outage a couple of months ago. I wonder if I could have sent them off to the DPI or something to have an autopsy?

Oh well, clean tanks, fresh food and try, try again.

Yep - can't hurt to do a full clean.

BTW, what do you regard as a mild solution?

Fish Kills
Can a fish die-off happen to you?
By Bob Lusk
I have seen several cases of toxicity due to aflatoxin from moldy feed. If you have moldy feed, don't use it.
http://www.bassresource.com/fish_biology/fish-kill.html

Pathology of Afloatoxin
High-level aflatoxin exposure produces an acute hepatic necrosis, resulting later in cirrhosis, and/or carcinoma of the liver. Acute hepatic failure is manifested by hemorrhage, edema, alteration in digestion, and absorption and/or metabolism of nutrients and mental changes and/or coma.
No animal species is immune to the acute toxic effects of aflatoxins including humans; however, humans have an extraordinarily high tolerance for aflatoxin exposure and rarely succumb to acute aflatoxicosis.
http://en.wikipedia.org/wiki/Aflatoxin

I think this is the cause of your losses. Low DO kills fish outright and there would have been signs of distress before this- surface gasping; stressed fish usually get diseases before they end up dying; the fact that you fed moldy fish feed probably poisioned them. The mold could have been caused by mice urine as mentioned above but most often, it is caused by having feed in a high moisture area. Feed of any kind should be used up in less than six months and kept cool but dry. Even the protein in the feed, which is usually a fish meal or fish oil source, can go rancid and again cause poisioning.
Check the livers of your fish and you will have your answer. If you don't know how, there may be a university or college that will do a toxicology for free. Call around- a lot of people don't know that colleges and universities do this type of thing but it is good practice for students. Also call your county extension office, often times they know places that may cost nothing or very little.
I would suggest cleaning out your growbeds, anywhere the feed settled and change out all of your water. I don't know how much toxin is required to kill fish or to stress them, which may lead to other problems in the future. Maybe the above references can help with that question as well.
Sorry for your loss. I think you are the first one here, that I know of, that has had this problem.