Backyard Aquaponics
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The first trout died early on the 25th November, the second one today, around 14.00H. I have this one trying to breathe while swimming vertically. I put it in a small tank of rain water, nothing changed.
Here is a few pictures.
air temp : 6°C, water temp : 6°C pH 7.0, nitrite = 0, nitrate = 80+

An idea of the problem?

I've replaced 200l of water (total capacity 1250 approx).

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Seriously - there is a LOT more information needed..

More of a story of what you have, and what you have done..

Naturally, we could pick on water contamination and ammonia issues, but it is ALL guessing at this time..

and the first thing I would do is add SALT to the isolation tank AND air, and where did the Rain-Water come from.. I killed all my fish with Rain-Water
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More informations about my AP :

750l fish tank

700 liters of clay balls in 2 growbeds (together 2,5 m²)

Chop type (made from 2 IBC), 1250 l of water in total

used rain water, air pump (840 l/H), circulation pump 2000 l/H

AS built in august & september 2015, fishes introduction end of september.

The fishes come from a fish farm (using water from a resurgence) located 20/25 km from my house. There is not much industry in my area so the air is rather clean. The area is full of farms growing mainly cows but also pigs, chickens...

I have already put some salt (about 30 g 15 days ago) and some sugar (5 g a week ago). I learned these things on Backyard Aquaponic site.

First I didn't put insulation around the fish tank, I did it a fornight ago. Now when I work around the FT (feeding, cleaning solids, etc.) they are more afraid ; they bump the IBC wall often, rather heavily.

It may explained why the second fish has a deformation of the head… ???

If something is not clear, please, let me know.

My trout and some similar white stuff on them after a yabby died undetected. Didn't realise the fish were impacted until I found the yabby dead and covered in a weird white film. Checked the fish closer and they had some kind of infection not dissimilar to the 2nd photo of yours but I added salt (1000l of water and sure it was a lot more than 30g...). That said none of the fish died during that period.

I did lose two fish, a week apart between each death that appears to be caused from a pH crash but then I see your pH seems fine. Have you test the water with both the high and low pH test kit?

When my 2nd fish died I performed a biopsy, nothing seemed out of the ordinary, the gills were fine as well. I have a large rectangular Black fish tank and they frequently can be heard bumping into the walls but haven't suffered the same fate as yours.

How many fish did you start with? How many in there now? First time I've read about adding sugar... I'll have to look that up now!

I don't have any answers for you as I'm new to AP and keeping fish myself but as I'm running trout thought I'd chime in if only to hear others opinions. I would do some regular water changes, then dose up with salt again perhaps after having all the water parameters checked to confirm your own numbers... Can't hurt.

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Yves16... where did the rain water come.from. ie how collected...

I am clueless at this time, but can identify with what I called Mush-Mouth, caused by fish smashing into walls.
That will. Certainly kill them in time..

As a perch grower said.. they usually take a number of days to die..

Perhaps that IS the cause... the dealers throw floating mats on their tanks to give the fish somewhere to hide..

Peter

Thanks for your concern.

I'm replying the 2 questions.

End of September I put 8 little trouts (30 g each) then 4 days later 10 pthers.

The rain water is collected from the barn roof; the gutters and the tubes are made from metal. It's supposed to be Zinc, but I really do not know exactly. I have to check.

What happens this morning : I observed 2 trouts swimming very slowly apart from the others (which were gathered in a corner having quick movements). I found 2 trouts deads one before, 1 after lunch; I almost sure that they are same since one of them was the smallest i had in my tank.

1st trout 80 g 19 cm (caudal fin included), 2nd trout 100 g 20 cm, 3rd trout 30 g 15 cm, 4th trout 50 g 16.5cm

I'm going to place a polystyren sheet inside the FT.

I hope to have fully answer the 2 posts.

I found this product on API documentation : API Nitra-Zorb (
http://www.apifishcare.com/product.php? ... lmpS7y350w)

Have anybody heard about this product???

Also, I forgot to answer one question about pH : I'm using a PHmeter (PH-900); I check calibration from time to time.

Yves, If I'm reading correctly, you now have four dead fish?
Zinc is toxic to fish, and it is possible that the rain water from your zinc/metal roof is toxic to the fish. Can you do water changes with water from another source? This may or may not be your problem, but it is worth mentioning.
The salt required to protect the fish from disease or nitrite in the water is minimum 2 parts per thousand, or about two kilograms into your system of at least one thousand liters/kilograms of water. Most fish are perfectly happy at 5-10 ppt, so do not worry about harming the fish. Strawberries and some veggies will not stand more than 2-3 ppt.

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I am concerned.for you, hearing the words Galvanised Roof..

That API product would not likely help, as it seems to be a nitrogen absorbing product.. probably Zeolite..
Zeolite will help with the Ammonia and Nitrites, but that is not likely your issue.

My first thought is that you may not win the battle and I would think the remainder are as good as gone.. I doubt you can reverse the damage..
So you seem stuck with your water collection.. you could look to PAINT the roof to reduce the zinc contamination ..
Just an early warning.. if using clay balls, they may be now contaminated and it will take a deal of water changing to get the Zinc back down..
A few on here have found that their media becomes a Zinc Store..

I would wonder if you could consider alternative fish eg. TILAPIA

My zinc contaminated system, now has Koi in it..

Sorry to give you bad news, and it is still speculation and difficult and expensive to prove..
I could not or would not gget tests done as it was going to be hundreds of dollars to test..

PS
I just revisited the original post and see FRANCE and 6DegC.. ie.. COLD..

Again, I feel you are done with these fish.. I feel (not scientific) , that the media absorbs the Zinc and absorbs and when saturated, the water then becomes toxic.. I suspect that we will have a deal of trouble getting it out.
I do hope that others will tell you that I don't know what I'm talking about, but.. but.. I wonder if WE could try Activated Charcoal

But.. your first challenge is to fix the water source..

My second system, is more a RAS.. A fish only system and the solids will go to the plant growing system ..

I would love to hear of scientific evidence that Activate Charcoal, will remove Zinc..
If it does, then that could be a cheaper answer than painting the roof.. ie.. you could filter the rain water storage, AND, filter the fish AP system, but my concern with filtering the AP system, is that the charcoal seems to filter. EVERYTHING, including nutrients..
So removing Zinc from the system may cause the whole system to crash, but this is something you may have to do..
I am assuming that the Zinc, absorbed into the media, will leach back out, as you suck that zinc from the water.
Yav also had this problem and like me, found that even 100% water changes, does not fix the problem..

Sorry that the speculative news is so bad..
.. Peter

I first corrected the title since 4 is now the right figure.

Due to my not so good english (that I hope you'll excuse), you think that my roof is made from zinc sheet. Not at all it is made from tiles (made from clay). Only the gutter and the descending pipes are made of metal (I still have to know which one). The water does not stay in contact with the metal; i agree that, in time, some zinc molecule goes into the water.

Early this morning it seems that the trouts had become as normal as before (except maybe the biggest one), I gave them little food.
By now, they have become "restless". I don't know if the word is good, i mean that they seem very nervous with quick swims in every direction.
I've to search the Backyard site because I think to remember that some people already made about the same comment.

I have replaced again 200 l of water.

I'll keep you posted.

Hiya Yves, it has been two months since you started your system and fish have been OK in this time so unless something has changed around your system recently it would point to a cumulative issue however I'm not convinced it is a zinc issue especially if it's clean rainwater with a neutral pH as your water test suggests.
What did your ibc ft previously contain? What are you feeding the fish and how much? Do you have any copper in your system? What kind of pump are you using? What air hoses are you using? And is it constant flood?
Sorry about the questions I'm just trying to rule a few things out.

No problem with the questions, i'd like to understand what's going on.

IBC : I do not remember since i have several IBC, I believe that it's contained flocculation agent used in a water treatment plant.

Copper: none

Pump : Duramaxx max flow 4500 l/H (but it is running at half flow rate)

air pump : JAD modl S 2000 with teflon pipe (I believe) and 2 stones

constant flood : Yes, the water goes from the top of the FT to the growbeds (with auto siphon) then to the sump tank where is the pump

I've checked my pH in 2 spots (2 different roofs), I've found 7.1 and 7.3

Today, I've read the artical about the removal of solids from Gary; it might be the cause.

As I already said, I remove solids by hand, in fact, I'm talking about the visible solid. I have noticed that inside the first GB there was a kind of mud on the spot where the water drop down from the FT. This mud tended to retain some water.
You can see on picture "a" that water tends to form a kind of"pond", on picture "b" you can see the dark place of clay peblles full of water.

I've changed clay pellets (not all of course) with new ones, placed mechanic filter (200 µ) at the water exit (both growbeds), cleaned the GB at much as possible with new water (i get rid of the washing water) and changed once more 200 l of water.

Since the 29th of November, I lost 2 more trouts for the same reason: the nitrates (99% sure of it).

One of the problems is the imprecision of the API colored chart showing the nitrate rate above 80. In fact the nitrate rate in my system has probably gone above 100 or maybe 150(???). At that time i'd checked nitrites & nitrates once a week; nitrite has always been good, nitrate has gone from 40+ to 100++ very quickly due to my faulty GB and i've underestimated the good one.

Now the water is going through only one GB (I've isolated the oldest GB where I saw 'silt"). I've changed three times 300 l of water. I'm back to 40 for nitrates.

The 12 remaining fishes eat again since 2 days (they had stopped around mid december). I'm preparing a 120L biofilter; I'll make quickly a mechanical one.

And i still have to cleaned the second GB before to put it back in use.

Thanks for all the information you have given to me, I hope that problem is over.