Epic Failure – Devastating Blow
Last week I was reminded how fragile the balance in an aquaponics system really is. I look forward to feeding the fish every morning before I leave for work. While I am out at the aquaponics system I also check on the plants, of course. It usually is a few minutes of joy and tranquility before I dive back into my long commute and long work day. Well, that expectation of tranquility was quickly wiped out by total disbelief, shock and panic. While I was walking up to the system with the little plastic container of fish food in my hands I suddenly noticed that the entire water surface was littered with dead fish floating upside down. It hit me like a lightning strike, like a bad dream.
I couldn’t believe it. Everything was working so perfectly for the past eight months, with the exception of a few start up problems, which I had anticipated. I was so proud of my tilapia colony of close to fifty fish. Sure, I was concerned with the amount of fish in such a small tank (250 gal), but I had done my homework and calculated my biomass (number and weight of fish) compared to the available bio-surface area for the nitrifying bacteria to thrive on. I had tested this again and again with my water chemistry test kit. My ammonia and nitrite levels were near perfect whenever I tested them. I even loaded up the system by feeding the fish five times a day over one weekend to see, if the biofilter could keep up with it and it did.
So what had happened? Why did so many fish die all of a sudden? How many were still alive? What caused this devastation? At this point I was sick to my stomach. I was about to fish out the floaters when I noticed that the water circulation through my filtration system as well as my heating system was non-existing. My aeration wasn’t working either. The system had no power whatsoever. Then I remembered that there had been a major thunderstorm the day before. I wasn’t in town when it happened. My workplace is 65 miles away and it was sunny there. Other thoughts rushed through my mind. What if lightning hit the system and electrocuted most if not all of the fish? I looked for signs of that, but couldn’t see any. I checked the electrical outlet to which the extension cord was plugged in for the system. The outlet has a GFI circuit – a ground fault interrupter. This is a circuit that trips when there is a small leakage current between the hot (phase) and earth ground. You’ll find these circuits in wet areas, like the bathroom or the kitchen, or any outdoor circuits. The GFI had tripped, indeed.
Now I started to wonder, if I had a ground fault in my system somewhere. Resetting the GFI circuit and sticking my hands into the water may have not been the smartest thing to do. So I left the GFI tripped and thought about the potential root cause some more. In my head I started compiling a list of possible candidates that could have caused a ground fault. There are three pond pumps submerged inside the fish tank and one heating system with a 1,400 Watt heating element. I checked the heating system first, since it was most accessible. There was no water ingress near any of the electrical connections. I opened up my plastic containers that are all housing timers and other electrical outlets, thinking that water may have entered somewhere there, but nothing. Then, while taking a step back, it dawned on me. I had left another electrical extension cord plugged into my system. Nothing was plugged in to the other end. It was lying on the sandy and still muddy ground next to the fish tank.
I remembered having similar issues with tripped GFIs during Christmas time with extension cords lying in wet grass outside. I was pretty certain that this was the cause for the power outage. There was actually some water left inside the female plug of the extension cord. At that point I just knew that this was it. It rains very rarely in Southern California, especially in the summer. I did not think about unplugging that extension cord, but by now I was really regretting that decision. The level of regret increased with every dead fish that I removed from the tank, not knowing how many got killed. At this point I knew that none of them actually got electrocuted. Then doubt set in. Why then did they all die that fast? The storm was the day before. All that had happened was that the filtration system, the aeration and the heating system had stopped working. I checked the water temperature and it was still 72F, which is perfectly fine. It is set to 78F with the heater. I then checked the water chemistry and that’s when the second shock hit me. The ammonia and nitrite levels were off the chart. Ammonia was beyond 8ppm (end of measurable range) and the nitrite level was beyond 5ppm, also beyond the measurable range of that kit. 8ppm or more is lethal.
Now, tilapia can withstand quite a bit of an abuse when it comes to bad water quality. The number of dead fish, judging by what I could see as floating fish at this point was telling me that the ammonia and nitrite levels must have been at least 2x or 3x that. I was in disbelief. How could 16-18 hrs of missing bio-filtration wreak havoc like this? I figured now that I had the filtration running again, the water quality would quickly improve. Plus I had to go to work. At this point I had spent two hours on the system already. I tasked my kids to keep an eye out for more floaters. I had just made it to work and there was the first text message from my daughter. “Daddy – three more died!!!”…then another one an hour later and the text messages kept coming in. After several additional devastating text messages I instructed my daughter to pour in a pound of aquarium salt to counter the effects of the ammonia on the fish.
High level of ammonia prevent Oxygen to enter the fish’s blood stream through the gills. This causes “brown blood disease”. Essentially, the blood coagulates and turns into a thick brown goo, which leads to organ failure and suffocation. Regret now turned into guilt, since I had left the extension cord plugged in. After the salt treatment, the fish were still dying. I couldn’t concentrate on work anymore and I decided to drive back home in an attempt to save the rest of the fish. I got back home around 3pm. I stopped by the local hardware store and picked up two 25gal buckets to put the survivors in. When I arrived, more fish had died. I took a sump pump and emptied the entire fish tank, only leaving a few inches at the bottom. Then I climbed in with a fish net and some remaining hope. In the end I was able to save 27 fish total. To my surprise I found 6 gold fish as well that I had used in the beginning to start up my system. I thought these had long died. All of my larger fish didn’t make it. Well, at least I have 27 fish left. In order to verify my theory about the ammonia and nitrite levels, I put 15 fish into one bucket and the rest into the second bucket. I then took a water sample every hour. The ammonia level increased by 1ppm every hour. This was with rather small fish, but also with a lot less water volume. Nonetheless, this demonstrated how important the bio-filter is for such a system. Especially with the water volume to fish ratio.
The lessons learned:
1. Never leave an extension cord plugged in and lying on the ground, unused.
2. The system cannot survive for more than maybe 6-8 hours without bio-filter, depending on the biomass.
Well, #2 is a real problem. I need to work on a contingency plan to avoid this from happening again. What if the pump fails for the filter? What if the plastic box brakes that makes up the filter? What if there is an electrical black or brown out?
I am currently working on a micro-controller that will control and monitor my system conditions. It will be Arduino based. More on this subject in future posts. I will also add a battery backup system for the bio-filter pump…so that I can sleep and travel in peace again.