View Full Version : Tilapia not eating despite good water conditions, help!

01-16-2014, 12:37 AM
Hello fellow aquaponists:

Recently, I have experimented with a new system (i.e. grow towers above a single fish tank that houses the fish and water pumps, see <http://www.aquaponiclynx.com/WordPress/wp-content/uploads/2011/03/t100-1-Medium.jpg>) and have experienced totally mortality of all my tilapia despite maintaining key environmental factors (i.e. pH ~6.8, regular removal of solid waste, ammonia 0ppm, nitrate 80ppm, nitrite 0ppm, temperature ~22-24 °C, new system was situated in heated indoor environment). Below is the timeline of events:

1. In the new system, I cycled the water and there were no nitrites and low levels of ammonia; as well, nitrate levels were increase suggesting that the key nitrifying bacteria had become established in the bio-filter.
2. I transferred 11 fish (i.e. ~5” in length) from an old system to the new system.
3. A couple days afterwards, key environmental factors were still being maintained but the tilapia had not been eating any of the fish pellets they were fed. The tilapia continued this behaviour until their death.
4. Two months later, I discovered one of my tilapia had died. Then subsequently over a course of fifteen days 10 more fish died. Within this time, we tried to improve the situation by cleaning the tank, changing the water in the system, and reducing feeding frequency and the amount of feed. Upon inspection of the external surface of bodies there were no signs of physical trauma or pathogenic infections.

I have several possibilities, which are not necessary mutually exclusive and there is not a clear cause and effect relationship, as to why my tilapia may have died:

Psychological shock: When the tilapia were transferred to a new system, which may have caused the tilapia to lose their appetites. As a result, they starved themselves and made them more susceptible to pathogenic infections.
Environment shock: Environmental factors, other than the aforementioned water conditions which are at acceptable levels, may have caused stress, e.g. psychological shock, to the tilapia in the new tank.
Nitrate shock: Moving the tilapia from an old system with >160ppm nitrates to a new system with much lower nitrates may have stressed the tilapia. As a result, they starved themselves and made them more susceptible to bacterial and pathogenic infections.
Electrical shock: Electrical leak from electrical components in the fish tank may have “shocked” the fish so much that they became psychological and/or physiological stressed.

I know this system can work because others have purported it to be the case. If anyone has any insights on this issue and could help me, I would be very grateful. Especially any ideas on why the fish would not eat anything.

01-16-2014, 08:23 AM
I'm fairly new, my thought is either heavy metal toxin or contaminated fish food. As for stress or water I don't think so, from my pass experience I would say that I stressed my fish to the MAX. MY tank pump float jammed...to make a long store short. I lost about 840 gals of good fish water when my 850 gal tank lost all but 3/4" of water (check out "Metal Core on pump" by Apollo). It did slow their eating and activity down but only for 2 days, NO FISH DIED!

I know that the person I bought my tilapia from puts his fish food into freezer baggies then straight into the freezer as soon as he opens the large bag. As a safety precaution, says that it can spoil over time.

01-16-2014, 10:47 AM
Thanks Apollo.

My system is located is in Vancouver, Canada and heavy metals in the water supply are generally not an issue. I have also not used any non-food safe chemicals near the system so I don't think that would be one avenue in which my system received heavy metals.

I have thought about food contamination but I've used the same feed in my old system and those tilapia seem to be doing just fine.

01-16-2014, 11:24 AM
What was the temp? Changes in environment/water conditions does cause stress. Did you do anything during the two months that they were showing signs of stress?

Stress comes in many forms. But the symptoms sound like stress and lack of adequate heat. Even in TX I don't keep mine at room temp. Tilapia handle too much heat better then they handle too little.

01-16-2014, 11:26 AM
Electrical shock would have resulted in faster death.
Contaminated food would have resulted in different symptoms and a more clear defined cause of death.
If it was metal contamination, the water changes you said you have done would have dillouted it out.

01-16-2014, 01:36 PM
The temperature was maintained around 24-22 °C, which was the same temperature in my old deep water culture and media bed hybrid system where the fish are still very healthy and eating well. As for the two months prior to their death, they exhibit the following symptoms: lethargy, tended to congregate in a corner, and lack of appetite. When the same exact fish were in the old system they would race towards me when I was regardless whether I was about to feed them or not, but when I approached the same fish in the new system they were indifferent. Food contamination and heavy metal poisoning don't seem likely either because I have been using the same food to feed the fish in my old system and all those fish are still alive and well. Heavy metal poisoning does not seem likely because I had not used any non-food safe products near my systems and the municipal water supplies is known to be clean. Oxygenation was high at all times, ~6mg/l. At this point, I'm almost out of scientific explanations.

01-16-2014, 01:42 PM
I thought the metal toxin might be coming from your pump, heater or maybe a protected wire mesh covering.

I do know that my water temp was 62 - 64 though out my ordeal, not nearly as warm as I would like it. But the best that I could do, I did add a small amount of "API Stress Zyme+"


01-17-2014, 10:35 AM
Last time mine quit feeding it was a bacterial infection. Do you see any change in behavior just before death, swimming sides, gasping, sores? And the infection may not be apparent at onset, check the deceased ones very close for any signs of an infection. If you find any infection, quarantine them and treat with Tetracycline, available at most farm supplies. It's listed for birds, but works equally well on fish too. I don't remember the dosage off the top of my head, but I can get it if you need it. I lost about 8 fish over a week before I was able to diagnose mine.

01-19-2014, 02:44 AM
The pump, heater, and mesh don't seem likely candidates because I've used them in my old tank and the fish there are happily swimming. Prior to their death, the fish were lethargic and indifferent towards food. No external body surface indicators would suggest pathogen infections or physical trauma. But I will look into API Stress Zyme+ and Tetracycline.