Backyard Aquaponics
A place to discuss aquaponics

My IBC Aquaponics system has been up and running since February, 2015 and over that year and a half, I have never been able to keep fish alive for more than a couple of weeks.

The system consists of one whole 330 gallon IBC tank for the fish, 2/3 of a 330 gal. IBC tank as a sump, and 3 grow beds made out of 1/3 of a 330 gal. IBC tank each. I have also added a swirl filter, made of one 30 gallon plastic barrel. My grow medium consists of about 1/3 volcanic rock and 2/3 expanded clay pebbles. It is plumbed with 100% PVC and uses only one pump. Water is pumped from the sump below ground level, up to the fish tank where it then overflows and is gravity-fed to the grow beds. I estimate there to be about 650 gallons of water in the system.

Initially, I dismissed the fish deaths as par for the course in an unestablished system, and accepted the deaths as part of the process of getting the biological filter and chemical levels right. A year and a half later, I am convinced I must be doing something wrong.

Plants thrive when I do have fish alive in the tank, and even survive with just water flowing & no fish-nutrients. Whatever is causing the fish deaths does not seem to be detrimental to the plants.

In Florida where I live, I do not have a problem with water temperatures for the tilapia and koi that I have been trying to raise. I have dutifully checked pH, Ammonia, Ammonium, Nitrates and Nitrites, and have never seen a problem with the levels. I have never observed an Ammonia level above 0.25 ppm. At first I assumed that the flood/drain process with bell siphons was providing enough agitation/disturbance of the water to maintain sufficient dissolved oxygen levels. Given no obvious spikes in ammonia however, I began to focus on an oxygen deficiency as the problem.

After maybe 8 months with no fish in the tank, I have added multiple oxygen sources. First, I added a delivery pipe to the fish tank filled with 30-40 small holes to force the returning water to splash violently into the surface, creating bubbles and adding oxygen. The dozen fingerling koi I then added were dead within 48 hours.

Next, I added two air pumps (One of which was advertised to oxygenate up to 1,000 gal. ponds), with a total of 4 large airstones. I drained and replaced 50% of the water before introducing another dozen fingerling koi. They seemed to do well for about a week and a half. Then 8 of the 12 died within a day or two. I changed 50% of the water again, and I think I have 2 or 3 fish still alive.

I am at a loss. I’m frustrated and disgusted, and I have nowhere to turn for help.

Before the fish die, they seem listless; even drunk. They swim upside down and sideways, and just generally act unusual. This seems like it could be the result of a lack of oxygen, too much ammonia, some sort of contaminant, or even some sort of infection/illness.

As far as potential contaminants, there are only 3 things that come to mind…

1. The IBC totes themselves. They originally contained a non-toxic substance – shampoo. It had a very strong coconut smell to it, but I took great care to clean them, even pressure washing them clean and there has been no evidence of any of the former contents for a year and a half now. I thought I understood that as long as the containers were not used for toxic contents, they could be sufficiently cleaned and used without problems.
2. Pressure Treated Wood. On the fish tank, I screwed some small pieces of plywood into the top to attach a lid with hinges. Can pressure treated wood kill fish?
3. Metal. The hinges and screws while small, do come into contact with the water. Can this little bit of metal kill fish in a 650 gal. system?
4. How about food? Is there something wrong with feeding them the bulk fish food I buy at the local feed store? Or the cans of Hartz floating koi food from the local pet store?

…Or do I just need to focus more on Oxygen? Buy a good, quality agitator like I see at the fish farm / bait stores?

Any help or advice you can provide is greatly appreciated.

Welcome to the forum . Sorry to hear about the fish, sounds like a pain. Pressure treated and some metals can potentially cause problems but I don't know if either caused yours.

Hi and welcome post up a few photos of your system it may help
Do you have any copper in the system

wood - yea CCA wood will kill fish, but i also have a little holding down my liner to my FT and not even babies die, try to minimise the amount. if you remove the wood, change the water out.

metal, i ran 2x galv. water tanks - 2500l each - and would get zinc levels of about 1.8ppm, this was enough to kill trout but not goldfish, although i still managed to always have one or 2 trout live through to harvest. - trout are super sensitive. I dont think it is the metal..... you dont have copper in or above the system i hope.

oxygen, it isnt oxygen or you would have some left, as the numbers die down the oxygen levels should balance out.

Shampoo is toxic to fish, but shouldn't be a problem if you have successfully removed all traces of it.



Deadly to fish if it contains Copper Chrome Arsenate and traces of it get into the water. It is also very poisonous to humans



What sort of metal? If Zinc plated and in contact with acidic water, then Zinc will end up in the water, and for fish it is very toxic.

Oxygen levels should be fine if you have an air pump running.

No copper in the system.
I will get some pics posted shortly.
Thanks!

I may do just that. Not sure what I could use in olace of it, but the wood & hinges could both be eliminated to narrow down the problem. Any idea whether hardy board would be a non-toxic alternative to pressure-treated plywood?


On this note, the one fish I had been watching swim like it was drunk over the last few days finally kicked the bucket. I now have two fingerling koi remaining & both of them appear healthy and happy this morning. I'll give it some time, but I'm not exactly dismissing oxygen just yet...

Honestly, I do not recall whether the hinges are zinc plated or not. I think this weekend may find me removing any plywood & replacing the hinges with stainless steel. And if my 2 remaining fish don't make it, I may as well be cleaning the tanks and replacing the water.

Thanks!

Usually when it's oxygen they'll be gasping at the surface before they go so it doesn't sound like oxygen, more like a toxin or a disease but probably a toxin based on what you've mentioned already.

hey before you remove the wood or do anything drastic... try your water. get some of the water and some small goldfish or any type of fish you can get ahold of thats inexpensive and try them out in a small aquarium or make shift aquarium (something other than your system) and it doesnt have to be very many fish. the first time i ever did anything with fish i started with cheap goldfish from walmart for $0.10/each. $5.00 got me 50. if it is feasible for you to go this route, i recommend it. if they are dying like that in your water in a separate tank, then its your water. then try a different source of water.

hope it helps and i hope the best for you! keep us posted. this is quite interesting. thanks!

Pictures of system attached...
Behind the lid, displaying the return flow spraying out of holes in pvc pipe, plus another strip of plywood to which hinges are screwed in from top of tank


Lid wide open, displaying some small pieces of pt plywood & screws that keep the lid from falling into tank.

Rusty ol' hinge on lid next to pvc return flow from sump ...not so rusty 2nd hinge where it doesn't get as wet . Also some calcium/lime deposits from well water.


Fish tank & swirl filter


Plain ol' flood & drain beds


Siphon outflows to the sump tank (Buried underneath the grow beds)

Someone recently, in another thread, mentioned that you shouldn't cover the tank too much, because excess nitrogen needs to gas off and it can't if the tank is sealed, or nearly so. It may not have been nitrogen, I can't recall, but it may be something as simple as having the lid on the tank. Just a thought from a newbie.

looking at that calcium build up, could your water be too hard??

that isnt much plywood, i thought you said plywood lid..... it isnt the wood, however try to stop it sitting in the water when the lid is closed (it looks soaked as if it was just in the water)
it is highly, highly unlikely to be the hinges, as i said, ive had more sensitive fish live for longer in metal tanks.

That inlet pipe wets down that piece of treated wood in the first photo? stop that from happening.

if it were me, i would be assuming the shampoo might have something to do with it.
do you have access to enough water cheap enough to dump all of that, rinse the system a few times and start again with new water?

Plywood glue? Not sure if it is toxic?

What about cutting a piece of plywood to sit on top of the cage? You could hinge it from cage and being up off the tank there wouldn't be water contact and there would be an air gap to allow for gas exchange. Just throwing it out there...