Backyard Aquaponics
A place to discuss aquaponics

I picked up 80 trout last Saturday, four days later only 2 survive.
The only accurate test equipment I have is amonia, today that records about 0.3 which may be related to having dead fish or fish food on the bottom. I have added fish plenty of time in the past and know how to prevent the amonia spike at the start of the season. Water temp is around 15-18C. I am going to take a sample to work tomorrow and use the hospital urinalysis machine which will tell me the ph, nitrates, and if I am pregnant.
I've had no fish for nearly 3 months when the hot weather killed the last of the trout. When the trout died some of them stayed in the bottom of the tank for a while and rotted, leaving excess gunk in the water for a while and a lot of extra gunk being pumped into the grow beds. Since then the system has continued to run and grow veges. I have occaisionally added some humonia to feed the biofilter bugs although there is probably enough "stuff" in the water and grow beds that I didnt have to. The water looks and smells clean but there is a small amount of gunk on the bottom of the tank but that's always been there. But yesterday I noticed a large amount of gunk in the grow beds, so much so that is I dig down a little my hand comes up fairly dirty. There are lots of worms in both the grow beds and the bottom of the tank. There's a large air pump an plenty of splash coming from a bleed off of pipe from the pump. It's unlikely that any poison has been sprayed in the area, i havent been using any, and the neighbour doesn't even pull up any weeds just mows them once a year.
The only thing that comes to mind is that I havent added salt for quite a while, and I have had a couple of accidental water changes since the last salt went in over a year ago.
I recently obtained a blue barrel and plan to make a swirl filter in the near future to remove excess solids. The solids come from having too many fish, and the break down of organic material (eg old roots) in the grow beds.

I'd be curious to know what the experts think before I go off buying more fish.
Could it be that a pathogen has entered the water when the fish died in summer, and stayed there until now?
Would the probably 0 salt level made the fish more susceptable to disease?
Could the build up of gunk in the grow beds be causing too much of a problem?
Has anyone considered leaving the system in "fallow" for a year i.e. not having any fish and letting the grow beds clean themselves up (with the aid of worms and plants)

I will post again tomorrow night with the water test results

The biggest question would be what the PH is.

Answering the PH question will answer if your system remained cycled or you should have treated it as a new system.

In hind sight salt would of been must I think...even if only at 1ppt for proventive measures.

sorry for the loss KE

KE where did you get the trout from? there has been some discussion of easter states trout form a farm dying because the ph difference is too much of a shock . .

A quick water check on the hospital urinalysis machine
ph 5
nitrites 0

Would this ph be enough to kill the fish? I suspect it's quite a bit different from the creek water they came from!

Yes to all questians also at ph 5 your bacteria would have died so you will have to cycle your system again

holy smokes thats acidic!

That is scary. Checking the ph before you got the fish would have been a very good idea. I will be asking the ph of the water my forthcoming trout are coming out of so I can adjust if the diff is large

How the hell did it get to 5?

someone must have divided by zero

Almost all my systems are below 6.... And no problems....

5 is still within the normal range for rainwater - only just, admittedly, but still not counted as acid rain.

Fish will start dying at 4, but remember it's a logarithmic scale, so 4 is 10x more acidic than 5.

Rofl and well ?????
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yes mine are to but i bet the fish came with a ph of around 8 thats the killer

I doubt that the change in Ph has anything to do with your fish dying in a direct way. I reguarly move trout fingerlings and fry from my re-circ tanks (Ph of 6) to ones that are flow thru with dam water (Ph 8.5 in summer) and dont even bother to acclimatise them. I have never noticed any discomfort to the fish in any way. The last few years I have dropped off thousands of trout fingerlings into people's tanks and to the best of my knowledge not one fish has died due to the change in Ph. I dont spend long acclimatising them either as with Trout I have found its just not needed. The only time I noticed some discomfort was when the tank the fish were going into had a Ph over 9 and I was informed later that none of the fish died.
Think about what happens in nature. Trout like Salmon reguarly move from the Ocean which has a Ph usually over 8 into freshwater streams where the Ph can often be 6 ish.
If the Ph is the cause of your fish deaths I feel it would be in an indirect way thru increasing the toxicity of ammonia or some other chemicals.