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Hey team!

I usually like to figure stuff out myself but I guess this forum is here to help!

The last few days a few of my blue tilapia fingerlings have been dying mysteriously....here is the break down

800 L tank...the same of grow bed
All water quality tests normal, ammonia 0, nitrite 0, nitrate 5-10, ph 6.5
58 fish 2-3 inches feeding 42% protein trout food, all been eating except the 3 that died who turned pale grey and sank over last few days. Gills and major organs seem fine and no sign of lesions or disease. Plenty of aeration from bell syphons and recently added air stone...although a few times I have seen them gulping at surface after a bigger feed but pretty confident it's not a DO problem

These guys were troopers during cycling and only now when everything is doing so well I start losing fish??

Any ideas would be appreciated! Do I just put this down to weaker fish dying off? I have an aluminum screen over drain would this be an issue? Grasping at straws peeps!

Thanks in advance!

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Forgot to mention temp range is between 70-80...trying to get a little higher now

Just starting myself,and I started my blue tilapia 6/8/13, one of the ideas I used was to make a jet sprayer from my sump,out of 1/2 inch pvc. caped the end drilled holes down a straight  line ,small holes, it really mixes up the water .

  

   good luck to you and yours

   Aubrey

To add to Nathan's Discussion:
I got my fish the same time and place as Nathan. Mine started dying about 3 weeks ago, 1 or 2 a day, then maybe nothing, then more dead the next day. Most of the dead guys have looked fine, however during the last week a couple have now had lesions on their sides..... dissected a couple and they haven't had any food in their bellies. We salted the whole system and have put the fish in a salt bath but hasn't done any good. We have lost about 30 now.....The closest guess we have at the moment is dropsy but we have no idea what's happening.

Water quality/temp is fine. They have grown really well and always ate fine, (feeding trout food).

Thanks for any ideas!

if you cycled with the fish, they could have been stressed by high ammonia or nitrites.. so fish become more susceptible to injury/disease.. and will die over time, not necessarily during the spike..
did you have a spike of any kind with the fish? what level have you salted to?
I had a mild ammonia spike followed by a week long nitrite spike no higher than 4ppm...I changed water, added salt and didn't feed and fish seemed fine...I do hear what your
saying Keith and could be likely...I now seem to think it may be streptococcus :( so any hints on dealing with the potential of this aside with keeping water quality at its best would be hugely appreciated!

Hi Keith -
No spikes for me. I had already cycled the system previous to picking up the tilapia and there had also been about 100 feeder fish in there for a couple months. 2 weeks ago I added salt to the whole system of 3ppt. Previously I had also given them a salt bath for an hour of a higher concentration. Yesterday I quarantened one of the tanks from the system and am planning on leaving them in an extended salt bath for a number of days if any survive. I started at 1ppt and thought I would increase it daily up to 6 or 10ppt.

Since Nathan and I got the fish at the same place and time, and now have the same thing happening (plus we started our systems differently) it leads me to think that it was either the stress of transporting the fish, or the fish had whatever it was before we got them.......but how to stop the die off????
Keith Rowan said:

if you cycled with the fish, they could have been stressed by high ammonia or nitrites.. so fish become more susceptible to injury/disease.. and will die over time, not necessarily during the spike..
did you have a spike of any kind with the fish? what level have you salted to?

Condolences Nate and Lanna:

I have seeing this same die off several times recently and and last spring, it seems to happen when the weather first warms up. 

After reading about your system I'm going to point to the obvious similar trait of the systems I see that have this mystery die off.  I would like to win one of these, so please follow along and report back, thank you. 

You have a 200 gallon/900 liter fish tank with 58 fingerling fish at one point.  The rule of thumb is one adult fish per 5-10 gallons of water in a commercial system.  They have lots of water flow, big grow beds, consistent plant loads, regularly serviced filtration and a knowledgeable staff.

You have a new relatively small system.  I know you were thinking when  you bought fish: "those are sure small fish"   Thinking that the system needed "big fish" you got lots of fish, since they were cheap and "so small"  That is the most common mistake I see.

I'm going to ask you to go back just 1 fish per 10 gallons of water or 20 fish in your system.  They will grow out right along with your plant load and your system will mature nicely.  "But I have 50 fish!" You say!  Yep! and you'll likely have 50 dead fish in a week or two. 

I coached a young man with this same problem here locally.  He had 100 fish in a 200 gallon IBC system with a flipped IBC lid filled with hydroton; sound familiar?   He came over this morning to buy new fish, all his original 100 tilapia have died.  He didn't follow my train of thought regarding salvaging a reasonable fish load. 

So now he has drained and scrubbed out his system and filled it back up with chlorinated water to kill everything and has it cycling again.   He is going to repopulate with just 20 fish.

I think what really happens here is the system becomes poisoned with the first sick/weak fish that eventually dies. It sinks to the bottom and you don't notice it until it floats to the surface.  Since it was undiscovered for days, the water is poisoned and has sickened the other fish by the time it is obvious something is wrong.

So:

  1. Scrub the fish tank and sump with a plastic kitchen scrubbie thing.
  2. Drain the fish tank 50% - dumping the wall stuff you just scrubbed loose.
  3. Check everywhere for dead fish and fish parts.  That includes the sump, grow bed, filters, fish tank, etc, everywhere. and flush the pipes with the garden hose.
  4. Refill system with out-gassed water, don't add anything else, don't worry about salt or pH, the plants and fish will be fine with the local water for a long while.
  5. Take out all but 20 fish.  Put the extra fish in a barrel or something.  They will need a 50% water change every other day, find them a new home. 
  6. Take a sample of the original water to the pool store and have it checked for dissolved minerals, they do it free of charge.
  7. Consider adding more grow bed.  Rule of thumb says, 200 gallons needs 20 cubic feet of GB minimum; I think 30cf is a more reasonable minimum however.  It allows for changing plant loads much better, keeping your fish and water much happier over the different growing seasons.
  8. Check your system and get rid of all the metal below the water line.  That includes, valves, drain covers, screens, etc. 
  9. Don't feed your fish for a few days, then feed at a minimum until this die-off is truly over.  If you watch your fish, tilapia will suck up as much food as they can grab.  A few minutes later they spit out a few pellets.  If you have been short feeding the fish, those extra pellets will feed the slower fish just fine.  If you check back in 10 minutes and there is food floating on the surface, scoop it out. 
  10. Continue to change out your water 30-50% daily for a week and then again every other day for another week. Gotta flush the nastiness out.
  11. Your water temperature is just fine, keep it above 60 in the winter if you're growing tilapia.
  12. Add another handful of compost worms, they eat the nastiness from the grow bed.

Good Luck!  You'll need it...


Thanks so much for the list Jim.
I have about 950 gallons total water in system with 80 cubic ft in grow beds. I have fed the fish minimally since they began dying off. They are still getting lettuce though which they devour. I will take your advice on the water changes in the quarantine tank. The last couple days I spent scrubbing everything I could.

We use rain water when we could, plus our well water (we let it gas off a day before adding.) We added a UV light 2 days ago, hoping to kill nastiness that might be in the water. I am still keeping my quarantine tank at 1ppt of salt. Do you think I should stop that if I am doing a daily water change?

I have a couple of pounds of worms in the gravel bed. I think the only metal would be the screens so I will see what I can do about something else.

I don't think we have a pool store, but I will try and find somewhere to do the water test. Our well water is really sulphery so it could potentially have high minerals in it.
Jim Troyer said:

Condolences Nate and Lanna:

 

I have seeing this same die off several times recently and and last spring, it seems to happen when the weather first warms up. 

 

After reading about your system I'm going to point to the obvious similar trait of the systems I see that have this mystery die off.  I would like to win one of these, so please follow along and report back, thank you. 

 

You have a 200 gallon/900 liter fish tank with 58 fingerling fish at one point.  The rule of thumb is one adult fish per 5-10 gallons of water in a commercial system.  They have lots of water flow, big grow beds, consistent plant loads, regularly serviced filtration and a knowledgeable staff.

 

You have a new relatively small system.  I know you were thinking when  you bought fish: "those are sure small fish"   Thinking that the system needed "big fish" you got lots of fish, since they were cheap and "so small"  That is the most common mistake I see.

 

I'm going to ask you to go back just 1 fish per 10 gallons of water or 20 fish in your system.  They will grow out right along with your plant load and your system will mature nicely.  "But I have 50 fish!" You say!  Yep! and you'll likely have 50 dead fish in a week or two. 

I coached a young man with this same problem here locally.  He had 100 fish in a 200 gallon IBC system with a flipped IBC lid filled with hydroton; sound familiar?   He came over this morning to buy new fish, all his original 100 tilapia have died.  He didn't follow my train of thought regarding salvaging a reasonable fish load. 

 

So now he has drained and scrubbed out his system and filled it back up with chlorinated water to kill everything and has it cycling again.   He is going to repopulate with just 20 fish.

 

I think what really happens here is the system becomes poisoned with the first sick/weak fish that eventually dies. It sinks to the bottom and you don't notice it until it floats to the surface.  Since it was undiscovered for days, the water is poisoned and has sickened the other fish by the time it is obvious something is wrong.

 

So:

  1. Scrub the fish tank and sump with a plastic kitchen scrubbie thing.
  2. Drain the fish tank 50% - dumping the wall stuff you just scrubbed loose.
  3. Check everywhere for dead fish and fish parts.  That includes the sump, grow bed, filters, fish tank, etc, everywhere. and flush the pipes with the garden hose.
  4. Refill system with out-gassed water, don't add anything else, don't worry about salt or pH, the plants and fish will be fine with the local water for a long while.
  5. Take out all but 20 fish.  Put the extra fish in a barrel or something.  They will need a 50% water change every other day, find them a new home. 
  6. Take a sample of the original water to the pool store and have it checked for dissolved minerals, they do it free of charge.
  7. Consider adding more grow bed.  Rule of thumb says, 200 gallons needs 20 cubic feet of GB minimum; I think 30cf is a more reasonable minimum however.  It allows for changing plant loads much better, keeping your fish and water much happier over the different growing seasons.
  8. Check your system and get rid of all the metal below the water line.  That includes, valves, drain covers, screens, etc. 
  9. Don't feed your fish for a few days, then feed at a minimum until this die-off is truly over.  If you watch your fish, tilapia will suck up as much food as they can grab.  A few minutes later they spit out a few pellets.  If you have been short feeding the fish, those extra pellets will feed the slower fish just fine.  If you check back in 10 minutes and there is food floating on the surface, scoop it out. 
  10. Continue to change out your water 30-50% daily for a week and then again every other day for another week. Gotta flush the nastiness out.
  11. Your water temperature is just fine, keep it above 60 in the winter if you're growing tilapia.
  12. Add another handful of compost worms, they eat the nastiness from the grow bed.

 

Good Luck!  You'll need it...

 

 

Hi Lanna:

That UV light will kill the good guy microbes too

Thanks Jim, will certainly try some of that...although my train of thought wasnt quite along those lines...my fish tank is only 1/3 full so am in process of adding more growbed and water...from research it seems a general stocking density has 1pd fish to 5 to 7 gallons so I'm pretty close to that mark I think

For sure going to take some fish out for now and do a big clean up...any idea what it is though Jim? Streptococcus??

Appreciated!

Can you think of anything that could be causing an increase in stress factors? Increase in light or lights being constantly turned on and off? Or maybe you have a toddler that likes to use your tank as a drum set?

I try and keep stress to a absolute minimum and cant think of anything recent that could be bugging them...my system is in a greenhouse so no lights, is mostly covered and have lots of pots for them to hide in...

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