Backyard Aquaponics
A place to discuss aquaponics

Hi guys,

I have a relatively new system here, water has cycled and then fish introduced into a 8ft x 4ft x 4ft fish tank (water depth at 3ft).

During the first batch of 500 fingerlings, it was probably my fault for not acclimating the fingerlings to my environment for a longer time. I had about 400 die off total (10 to 20 or even 50) every day for 10 days straight.

I got another 500 fingerlings and made sure I acclimatise them for a longer period this time. So that shouldn't be an issue. The average size of the fingerlings are about 1 inch.

Ammonia: 0 to 0.25 (never more than 0.5 at anytime)
Nitrite: 0
Nitrate: 35 to 45ppm
pH: 6.6 to 6.8 at all times
DO: 8mg/l ++

I probably would get advise from you guys not to stock too many the first time, which I realized now after reading much of the forum. But that's too late now.. and on top of that, I have also separated about 30 fingerlings to a smaller tank (4ft x 4ft x 3ft), as a control. However, those are also dying - so I don't think overstocking or lack of DO is an issue here.

My water seems fine from the stats above - what else should I test on?

Sometimes the fingerlings tend to come up to the surface like they're gasping for air, (even on the small tank, normally both happening at the same time) - I have no idea why they do that. I would then test the water in both FT for Ammonia, it would be 0 or 0.25, Nitrite is 0 as well.

Fingerlings are active - when I try to use the net to scoop up dead carcasses, the rest would swim away rather quickly. When I feed them, they rush to the food.

So far, I have not fed them for 2 days now just to see if it makes any difference. Besides water, the only other common denominator is the food. Tomorrow I will feed the smaller tank, and see if there are anymore deaths... any other ideas appreciated.

Some pic's attached on here... some of them are blind in 1 eye as you can see (eyes are all black). I took 2 random live fish from the tank.

Thanks in advance for any advise / ideas on what to do next..

Welcome to the forum injust

Sorry to hear about the fish. So that's about 720 gallons for the fish tank. Is what's left of the original batch still in the tank with the new group of 500? Sometimes if Nitrites spike without your knowing it the deaths can occur over a long period. You may just be seeing some of the first group still dying off from a nitrite spike. The spike might not have happened in the new system, could have been during transport.

To state what's probably obvious, the belly looks a bit sunken on one and the other looks like it had it's fin chewed off but I don't see any fungus indicating rot.

Hey scotty435, thanks :-) been a lurker here for a while now, but never got round to register and post.

The original batch has about 100 of them left - maybe just a little less.

Fin chewed off - probably bulling from the other bigger hungry fingerling - I seen a few bigger ones tried to "play" with the small ones. Maybe because I've been starving them for 1 or 2 days to see what's going on.

Articles I was reading seem to point to streptococcus as well, but they seem to swim ok to me. Any other signs of streptococcus I should look out for?

Is "stringy" feces normal? Long string of poo hanging out their ass - some of them maybe 3 to 5 cm long.

Thanks again :-)

I think initially it was probably a nitrite or ammonia issue but at this point additional deaths could be lots of things or nothing except stress and infighting. Salting to 1 ppt with salt that is not iodized and contains no anti-caking agents will help with the stress because it helps them build a slime coat. It also helps with nitrite toxicity which you no longer have (if you ever did). That's what I would start with.

Long stringy poo hanging out the back end is pretty normal for fish but 3 to 5 cm seems a bit long but I'm not a Tilapia grower so I can't say for them. What are you feeding them when they are being fed?

It doesn't sound like a streptococcal infection to me at this point and just from looking at the fish. It really wouldn't surprise me if it is a bacterial infection and that seems likely if it wasn't an earlier spike in water chemistry. Have you tried doing a dissection of some freshly deceased fish to see if there is any hemorrhaging? Wear latex exam gloves and dispose of everything in a safe way if you do this. Are any of the fish looking bloated do some have sores or abscesses on the outside? If you aren't seeing these in at least some cases then strep doesn't seem likely.

http://www.thefishsite.com/articles/190/streptococcus-in-tilapia/

If you still think it's strep then lower your water temp to 25 C and this should help reduce mortality.

Hi scotty435,

Today I just cleared another 50 carcasses. Yup I just added seasalt yesterday, about 250grams into the FT directly, which will be furtherdiluted by iincoming and outgoing water. I don't have a salinity meter now but have ordered one..but it wont be arriving so soon.

I did dissect the fish, when softly pressed near the belly, red liquid comes out of the belly, but I suppose all dead fish with it's guts still in is like that?

I don't see any sores outside. How do I identify a hemorrhage after dissection? Actually the ones that are barely dying, their belly do look bloated.

Can you check the colour of there gills,if you have any more carcasses.

Hey dasboot,

Some of them are pink, I checked 1 today that is barely alive though, this particular one is very red.

Most of the dead one the gills are pink.

Any idea why?

No pinks ok,brownish red would indicate Nitrite poisoning so you can rule this out,sorry this isnt very helpful at getting to the cause but its one to rule out.

I've caught 1 fingerling here that isn't swimming very well.. for this particular one, the gill is a little white as you will see in the picture.

But this might not be a good example (or it might be..?) because this was still moving, but almost at a 45 degree angle.


For a few minutes, I saw the fishes swimming towards the airstones, and then swimming away. and then turning back. And then many of them just trying to gulp air. But that just stays for 5 to 10 minute, and then they look fine again after that. I have videos of those but I am not sure how to upload videos...

Am I right to say that this would probably mean some sort of poisoning? Tested water again, that is taken from the SLO - so I assume this is water from the bottom of the tank.
Nitrite 0
Nitrate 40
Ammonia 0.25 to 0.5 (in between)
pH: 6.8

Found a way to upload videos:

Attracted to airstone for a couple of minutes: https://vid.me/y97R
and some of them going to the surface for air.

How "peaceful" and active they are:
https://vid.me/jYM5

Feeding: https://vid.me/m2Xj

What's the water temp?

Here are a couple of links that show what Petechial Hemorrhaging and looks like - it's the little pin prick red spots. Larger reddish areas indicating hemorrhage are probably what you would find inside the fish. The last link shows an example of this

http://www.portalveterinaria.com/apuntes/tilapia1.jpg
http://www.portalveterinaria.com/apuntes/tilapia2.jpg
http://www.fhs-afs.net/daa_vi_files/23.pdf

It helps to know what the fish should look like before you do this so that you know what you're actually seeing. Enlarged organs are another thing to look for. I'm also thinking the food may be too large for some of the fish and may be causing some of them problems. I'm basing this on the size guidelines from here - http://www.aquaponicsusa.com/products/aquaponics-tilapia-food.html. You might check the contents of their stomach to see if there is a problem. It sounds like they are getting food and are eating so it's just a thought.

Get yourself some latex gloves (I think harbor freight has them pretty cheap but drug stores do if they don't), some of these diseases can cause problems for people - Strep is one of them, it's not the worst and it's not likely but still, if you think they're sick it's probably a good habit to get into.

+1 on the water temp.

Where's Dr. Colum when you need him?

Thanks scotty435. I will dissect a couple of them today.

Water temp is 28 to 29 celsius.

I am located in the same country of the report you linked to coincidentally :-) I'm in South East Asia - it's not easy for me to bring the temperature down..

Thanks for the glove tip, I'll get a couple today.

I had a huge die off again today this was after I started feeding them yesterday.

Anyhow, I have removed all the fishes from the FT and placed them in a quarantine tank.
I've added some medicine (green colour liquid, made the whole hospital tank green) given by the aquatic store.

Some of the fishes when I pulled them out had their flesh ripped off - showing only the .. maybe a batch of 10 of them. I googled, couldn't find any disease associated with that - probably due to bullying?


Would like to get anyone's opinion, do you think I should do a complete water change?

Thanks again guys..