Dead Tilapia

[Moses Greengrass]

I really should be smarter and keep a better record of everything. On July 7th I added chelated Iron to my system because the plants were looking anemic which I think is due to high PH. July 8th the first floater popped up and since then 270 tilapia died. The dying stopped but the water is to murky to see any fish in there but according to my counting I have about 90 fish left. I have been testing the nitrites and ammonia and have been at zero ppm each time. I don't think a very small amount of chelated Iron could do that to my fish especially since I have almost 4000 gallons circulating through my system. I feel like I should have been more pro active in rescuing fish but I operate a small landscaping company and we have been busy. Regardless, this should have been a learning experience but it wasn't. I just counted dead fish for two weeks which doesn't seem very productive. Moving forward I would like to avoid any problems like this, but I'm not sure what the problem really was or is. I can start answering questions for anyone who is interested in helping me diagnose. I'm not very knowledgeable in the world of fish culture or aquaponics. Any help would be great!

[Sylvia Bernstein]

Wow...bummer, Moses!  I''ve killed a lot of tilapia over the past few years, and learned a lot so I might be able to help you.    One of the subtler things I've learned is that dramatic swings in either pH or temperature can kill them.  Have you, by chance, topped off quite a bit of your tank water with cold hose water on a hot summer day?  I couldn't figure out why I kept losing fish this past winter until I worked on it with Dr. Lennard in AU who finally asked me how I was filling up the tanks...and it ends up I was regularly swinging the temp 10 degrees in 10 minutes...oops

[Moses Greengrass]

I don't see a large swing in temp when filling for evaporation/transpiration. However, I am not heating the water and have my system in a greenhouse. At night the temp usually bottoms out at 65 and rises to 72 during the day. Certainly the fish want warmer water. Although I think disease is a factor. So many variables. I wasn't even testing the PH at the time but I'm pretty sure it went way up because plants went from green to yellow with veins on the new growth practically overnight. All I saw was an iron deficiency and did not think of PH.

[Chi Ma]

Higher temps = lower oxygen levels. How is your dissolved o2? The more densely stocked your tank is the more quickly things can go wrong.

[Kobus Jooste]

Moses - some indication of pH, temperature and the accuracy of your test kit would be very useful here.  If you think that your pH got so high that iron became unavailable, you could have been hovering at around 7.8 or even over 8.  Then, even sitting at 72 degrees F, your TAN (Total Ammonia Nitrogen) would start becoming toxic at readings around 0.5 ppm. 

[Kobus Jooste]

Chi - DO is possible, but with 4000 gallons of water and around 300 fish, the 72 degree F temperature will not ring an alarm bell with me unless there is a major source of decomposition in the system.  Tilapia can take really low DO and the system would have to be in really bad shape for such a large volume of water not to be able to have enough oxygen for 300 odd fish.

Chi Ma said:

Higher temps = lower oxygen levels. How is your dissolved o2? The more densely stocked your tank is the more quickly things can go wrong.

[steve]

Fish don't float up dead for awhile. Its probably been dead for at least a day or so before it floats up. So if a couple pop up there may have been 10 or 20 on the bottom decomposing in the water. So if you see a dead fish better look carefully for more on the bottom and get them out of tank. Sorry to hear this the bummer.

[Green Acre Aquaponics]

Sorry to hear about your loss!  I noticed you mentioned that your water was 'too murky' to see any fish in there and that is some cause for concern.  That may indicate that you had something anereobic occuring and my guess would be several fish dying at once.  As Steve pointed out, it does take some time for them to float and decomposition of multiple fish could contribute to poor water quality but would most definitely be reflected in high ammonia readings and it is odd that you were showing 0.  That is almost impossible  with dead fish in the system as dying, not only dead fish, will give off a lot of ammonia.  What kind of testing are you using?  A kit or strips?  Strips are known to go bad, so maybe you were getting some inaccurate readings.  You may want to perform a simple test by adding ammonia to some water and testing your test strips if that is what you were using.  A disease event is pretty unlikely in an AP system unless it was introduced from an outside source.   Unfortunately we all have some opinions on this because we all have been there.  I stopped counting how many we lost in the beginning!

[TCLynx]

You have almost 4000 gallons circulating through the system but you didn't say how big the fish tank is.  Some more details of the system might also help.

Fish tank size?

Grow bed type?

Grow bed/filtration size?

Pumping flow rate and schedule if using a timer?

Supplemental aeration?

 

And yes the testing methods?

 

What is your source water?

 

I agree that the chelated iron addition may have been totally incidental and you may have had a dead fish in the tank just not yeat floated up when you added the iron.  That fish would have spiked the ammonia and could easily have triggered many more deaths.

 

So cloudy water and dieing fish.  Question I haven't seen asked yet is...   Is there a build up of fish waste or uneaten fish feed in the tank?  This is the primary cause of fish deaths and opportunistic fish diseases in my personal experience, that or more lately I've had an issue with some spoiled feed giving me some issues.

[Moses Greengrass]

Basically my system is a water feature with vegetables. The fish tank is pond with about 2250 gallons, the water is skimmed from the top and bottom into a vault with bio-filtration, pumped at approximately 7200 gallons per hour into a 100 gallon stock tank filled with filter media which is my waterfall vault. The water then cascades into two 750 gallon grow bed reservoirs containing floating rafts, the water then cascades back into the pond by way of three waterfalls. There is six waterfalls and they are  providing my only aeration. I dug this into the floor of my greenhouse with a shovel and an unguided dream. Admittedly it is not the best design.

 

I have not been testing DO (not equipped)

Ammonia, Nitrites, and PH all cheap liquid test kits. None of them work I have realized and am out to purchase something new today.

Water comes from our well

 

I did find quite a large amount of uneaten feed in the water fall vault

 

I have not necessarily trusted my test kits all along and suspected ammonia. The only reason I have not ruled out disease is because of the place I initially got the fish and the strange snails that I assume came with them. The words "opportunistic disease" are key in that my balance and health of my system was clearly in downward spiral if and when any disease may have begun to spread.

 

Where to go from here? Can't let my rafts with all this good growth go just cause I killed all or most of my fish. But I do not want to repeat the massacre either.

 

Thanks everyone for all of your  input

 

 

 

 

TCLynx said:

You have almost 4000 gallons circulating through the system but you didn't say how big the fish tank is.  Some more details of the system might also help.

Fish tank size?

Grow bed type?

Grow bed/filtration size?

Pumping flow rate and schedule if using a timer?

Supplemental aeration?

 

And yes the testing methods?

 

What is your source water?

 

I agree that the chelated iron addition may have been totally incidental and you may have had a dead fish in the tank just not yeat floated up when you added the iron.  That fish would have spiked the ammonia and could easily have triggered many more deaths.

 

So cloudy water and dieing fish.  Question I haven't seen asked yet is...   Is there a build up of fish waste or uneaten fish feed in the tank?  This is the primary cause of fish deaths and opportunistic fish diseases in my personal experience, that or more lately I've had an issue with some spoiled feed giving me some issues.

[TCLynx]

Well, is the water clearing up?  If so, then see what your new test kit tells you and if the fish seem to have stabilized then you may be recovering.

 

Sounds like you have a good amount of flow so perhaps you just had an issue of perhaps overfeeding or the fish having gone off the feed briefly (and the excess feed being sucked into the filtration before you realized it) could have caused an undetected ammonia spike due to faulty test liquid (yea the stuff sometimes goes bad.)

 

If things are clearing up then the remaining fish could recover and you will just have to see how it goes.

 

It doesn't necessarily take a huge amount of fish to provide nutrients for the plants and if the plants seem happy then even if the nitrate reads 0 there may still be enough.

 

I've lately had some issues with some old feed going bad and causing system health issues.  I've disposed of the old feed and cleaned out all the feeders and bins and things seem better here since.

[Moses Greengrass]

My tests have been all reading zero, including nitrate. Plants seem OK, PH is too high for some. Algae is causing the water to be green. Trying to keep the light down on any open water. Occasionally I see one fish swim off into the green abyss if I sneak up real quiet. It might be the only one left. If I had one regret about starting up an AP system it would be that i overlooked this website before I built and started growing on the system. Thanks for all the knowledge.

TCLynx said:

Well, is the water clearing up?  If so, then see what your new test kit tells you and if the fish seem to have stabilized then you may be recovering.

 

Sounds like you have a good amount of flow so perhaps you just had an issue of perhaps overfeeding or the fish having gone off the feed briefly (and the excess feed being sucked into the filtration before you realized it) could have caused an undetected ammonia spike due to faulty test liquid (yea the stuff sometimes goes bad.)

 

If things are clearing up then the remaining fish could recover and you will just have to see how it goes.

 

It doesn't necessarily take a huge amount of fish to provide nutrients for the plants and if the plants seem happy then even if the nitrate reads 0 there may still be enough.

 

I've lately had some issues with some old feed going bad and causing system health issues.  I've disposed of the old feed and cleaned out all the feeders and bins and things seem better here since.

[Chris McMahon]

I read some where the warmer the water gets the more dissolved oxygen you need to have. Combine that with algae and I think Chi Ma may be on to something.