aquaponix

Hello from Houston, Texas....needing help with tilapia

9 posts in this topic

Hi all, I am in need of some expert help on why my fish are dying at a rate of 1-3 per day for two weeks now.  I am pulling my hair out trying to figure out what the problem is.  Let me give you all the particulars first:

 

I have been running an IBC tote system in a greenhouse for 9 months now (based on Murray Hallum's IBC system) which is a 275 gallon tank with three 4x4.5 foot grow beds and a sump tank.  I am using one pump to push water from the sump to the grow beds and fish tank. The fish tank return to sump tank is by gravity siphon and each grow bed is a flood and drain system with a bell siphon in each.  The grow beds have hydroton material as substrate and are currently full with tomatoes, green onions, swiss chard, arugula, cucumbers, kale and sweet potato(all greens with no potato).  I had around 50 (now more like 35) happy tilapia fish growing in my tank until around two weeks ago when all of a sudden I am experiencing fish death on a regular basis.  My levels are currently set at: PH 7.2 (this is the only variable that changed in the past month), AMMONIA: 0.25, NITRITE 0, NITRATE 80-100.  I run 7 air diffusers, with a cascading return from the sump tank to the fish tank.  The temperature of the water is around 85-90 degrees, but I don't have fish gasping for air.  I can see the bottom of the tank, so it's not a waste build up, yet I have been performing water changes every three days.  The dead fish seem to have a redness around their gills and when they are about to die, I see some swimming slower and listing to the side at the bottom of the tank.  I added about 5 kg salt to hopefully try and offset any stress they were experiencing, but don't see any difference in amount of loss.  I was wondering if anyone else have had these problems all of a sudden and what solutions or suggestions would be greatly appreciated.  Thank you in advance!

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If they are not fighting due to breeding,  then it's more likely a parasite.

 

http://www.massmind.org/techref/other/pond/tilapia/gills.htm 

 

Here are slides that show some different infections.

 

About the only thing you can do with food fish is a salt treatment.   The salt treatment is in a separate tank and for short duration.  I'm having trouble finding it, but Florida ag extenstion had a bulletin on how to do a salt bath.  The problem with that is that if the disease is in the advanced stages it can suffocate the fish by hardening the slime layer. 

 

I have read posts were it stopped as  suddenly as it started, but those were generally at the low end of temperature for tilapia <72F.

 

Welcome to APN.

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Hi and thanks for the link.  Since I have access to a microscope, I will definitely look into the parasite angle.  I guess the salt option is a good and bad, but I am trying to salvage what I have left in the tank.  I read that the redness of the gills is an ammonia issue but that doesn't seem to make sense with the low levels I have currently.  I wonder if the heat is causing a majority of the problem.

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Heat does increases ammonia toxicity , so maybe.  I've recorded temps up to 105F without major issue, so I don't think that is the problem as your just about Ideal water temp for tilapia. 

 

One thing that just came to my mind is that ammonia test kits go bad and give false low readings.  Had that happen to another member just a while back. He bought a new kit and his ammonia was through the roof.  His alkalinity had dropped and crashed the biofilter. Sometimes the kits sit on the shelf so long they go bad in the store. So it could be possible you bought a bad test kit.   Something to check.

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......and the time of the day in the case of pH.

 

If your system is based on the infamous CHOP2 design, then water quality is almost certainly behind the deaths. 

 

Your first move should be to get all of the flow from your fish tank going through your grow beds.....while you start to get some decent filtration happening.  I'd suggest a radial flow separator and a packed media/brush filter.

 

Your other option is to convert your system to iAVs......by replacing the gravel with sand....and investing in a digital timer.

 

Cut back on the food until you get the problem under control.

 

Gary

Edited by Gary Donaldson (see edit history)
Clint likes this

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Hi all, I appreciate the speedy responses from everyone and have taken the following steps:  I was not able to see anything eventful under the microscope, yet I am no aquatic veterinarian and the closest to me is 3 hours away and I have to bring in a live one exhibiting signs of stress to sacrifice for science.  Ravnis, I did take your advice and checked my water levels at the local petstore and they are exactly the same, so I can rule out faulty test kit on my end.  They did test my water hardness and it came out to 300, which I believe is pretty hard.  Not sure if this is a game changer or not.  Mhaigh, I did also take your advice and tested my water at the bottom outlet valve of the IBC FT and the levels were the same except for a minor adjustment on the nitrites going from 0 to .15.  I did install a circulating pump to stir things up a bit and to see if this would help with the temperature in the tank.  Gary Donaldson, I appreciate the suggestion, but I don't think I can make this adjustment right now due to funds and the design of my system.  It does seem like a better choice for reducing water and power usage.  I guess hind site is 20/20!  Anyway, again I want to thank all of you for your great suggestions and feedback to help me, I most heartedly appreciate it.  I have stopped feeding my guys and hope that my deaths will level out.  I did not find any other floaters this morning and have checked the pH in the morning and evening but it is constant.  So any other suggestions, would definitely be welcome and won't fall on deaf ears. Cheer!

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Could be gill flukes (Dactylogyrus/Gyrodactylus) which are parasitic trematodes, and quite common. They are in most systems at various times, but usually require a triggering event to reach a really high population level that threatens fish health. Salt treatments, accompanied with water changes usually helps to kill them off. However, seriously compromised fish often present with a secondary bacterial infection, frequently columnaris, which further weakens the fish. This results in several fish continuing to die following treatment, which can confuse the grower, thinking they still have a problem, when it is actually just the residual impacts of the initial infection and subsequent/secondary bacterial infection.

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Not a fish guy, but am in the Houston area and could show you how to build a radial flow filter in a couple hours and less than $100.  All need is a plastic barrel, 20-30 gallon, a 5 gallon pail, a few pvc fittings and some uniseals.  Message me with your number and we can talk it though.

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