Backyard Aquaponics
A place to discuss aquaponics

All my trout died over a period of two days starting Saturday.
I lost about 100

My system has been running for 18 months and has established plants and bacteria.
It is 4000lt and has a large air pump running continuously.

Over the past wee i have changed the following:
Hard pruned the tomatoes
Added 2 kg pool salt to bring the salinity from .3ppt to .9ppt

My levels are:
pH 8
ammonia .5
Nitrite .25

WTF has happened??

Your ammonia and nitrite levels aren't excessive... and are probably a result of any fish beginning to decompose...

What sort of aeration are you running... and what sort of pumping regime?

And what sort (brand) of salt did you add?

Sounds like something in the salt for sure DP

I had a similar issue last weekend.

For me it was solids buildup and lack of aeration. Check these, check your salt. Tomatoes are nightshades, so letting the pruning decompose into GB may be bad, but I doubt it.

Got to be the salt ,, OR neighbours spraying chemicals

How long were they in there for before hand? It's been a couple of months or so hasn't it?

Very possible! don't underestimate how far wind blown toxic chemicals can go. Just lost a nice mexican palm tree to the local government's ditch spraying program

The fish ahve been in there since April atleast EB

Duckies Air pump is the biggest possible one we could get from Vebas , running non stop , his tanks look like spa's . 100LPM I think

No neighbours near the tank , "nature" strip and then road ...

It HAS to be the salt , budget re-bagged store-brand salt , what could possibly be in it !?
Salt is salt isnt it ?

Hey Troutman , put me down for twice as many trout next year , they seem to keep getting pinched by people....

Salt ain't salt Boris...

When you say "budget re-bagged store-brand "... do you mean a "no name" house or cooking salt...

If so... it could be iodised or have anti-caking agents in it.... either way.... way badddd...

What you need when salting is seasalt... pure seasalt... most POOL salts are, but should be checked...

Many use "Sunray" pool salt, made by Cheltenham, available from Coles, IGA... Bunings (i think)... and many pool shops...

Solar pool salt or solar water softener salt (usually the cheapest ones actually) are fine so long as they are simply dried out sea water with not special rust removing, anti caking, or pelletizing agents. Table salt often has anti caking agents that can cause water to cloud (why you don't use plain table salt for making pickles etc.) Table salt is also often iodized which can kill off your bacteria. However, it doesn't sound like you added that much salt, only took it from .3 to .9 ppt Now if you took it from 3 ppt to 6 ppt that would be much more.

It seems the more common killer of fish when everything else in the system seems fine could well be the hydrogen sulfide gas that comes from stuff decomposing anaerobically. Are there any areas that tend to build up a heavy layer to gunk and get smelly? If so, stirring up some of that could cause a sudden die off. I have noticed that salting a system can sometimes cause some current changes as the salt affects buoyancy and causes some solids to re-suspend.

However the fact that there is lots of aeration kinda argues against the hydrogen sulfide poisioning unless the process of salting stirred up some un-aerated gunk from the sump tank or something?

Bummer, I hate sudden unexplained fish kills.

I reckon the salt had anti-caking in it

Here is another possiblity:

Is your air pump battery backed? Could it be possible that you've lost power for a couple of hours/half a day, one or two trout have died and gone to the bottom and manked up the water and killed the rest?

We all know the feeling, 40 trout died in 12 hours for me. I was watching them perish in front of my eyes.

THe salt is made by the only company in Perth that makes it. They bag it for everyone else so we feel we have competition.

I am sending the water sample to the local uni labs for analysis.
No smoking gun yet, butam leaning towards a salt addative

Was it a "kitchen/cooking" salt... or a "pool" salt Duckie?

The big "B" over east sell Sunray pool salt. It's ultra cheap and known to be ok, do "B" also sell this in WA?