Silver perch - fish deaths - Chemical say good???

boomahay

Hi all, hope you can shed some light here

Area - about 30 mins south of Ballarat.

I have two setups

1 - Is a split system filled with dam water with about 50 x one year old Silver perch. I have air stones in, and one grow bed. I have a bit of algae growing around the fish tanks, but the fish are fine and eating well, and the chemical test is pretty good. This system is outside and open to the elements. The temp can go from 4c to 22c at the mo

2- I have a 40 squire metre Polly tunnel, with pretty much the same system as above but i put rain water in it.

Problem - about 2 weeks ago I moved 2 x perch from the tank outside, and put them in the pollytunnel system. Because I added the media, the water was a bit murky and i couldnt see the bottom of the tank. about 4 days later the fish had floated to the surface, dead! (they did smell abit, and so did the water!

I drained the tank, cleaned the system and added more water from my rain tanks. I did a chemical test and all was good. I put two fish in and the next day they were dead too! Checked PH, Ammonia, Nitrite and Nitrate and all was bang on. I added more air stones and put 2 more perch in, the next day dead!!!

The medium im using is from an old system that i moved from a previous property. It was put in to a barrel, where it stayed for about 3 weeks till i started using it. can medium go off like this???

The temp in the polly tunnel is about 10c higher that outside. is this enough to kill the perch???

Has the first two fish that went belly up spoiled the system all together, and i have to rebuild the system???

My chemical test kit is about 2 years old. Can it show a wrong result after this time???

Hope someone can help out there?

Thanks

Allan

earthbound

Did the rain water come off a metal roof? This has caused problems for others in the past, zinc is highly toxic to fish.

Depsua

Perhaps the old media was holding a bunch of hydrogen sulfide after sitting anaerobically in a closed barrel for a few weeks? Subsequently washing the sulfide out by water changes and running the system, would not be pleasant for the fish.

joblow

As EB said, zinc is highly toxic to fish, not only the metal roof, are your rain tanks galvanized or PVC?, and as Depsua pointed out your old media could be holding hydrogen sulfide after sitting anaerobically in a closed barrel for a few weeks.

I have lost fish to Zinc in the past and flushed the whole system with 12% Hydrogen Peroxide and that fixed the problem.

Anything that has been used in my system that has been sitting around for any period of time, fittings, PVC pipe or clay balls, I always wash in Hydrogen Peroxide to kill off any nasties. I mix 1/2 a bottle of Hydrogen Peroxide in 60 - 100 litres of water and flush that through the system, or soak the fittings and clay balls in a barrel.

Use the strongest Hydrogen Peroxide you can get hold of, and the stronger stuff is usually food grade.

Nhibbo

Hi Boomahay,

I know this is an old thread, but just wondering if you sorted the problem.
I also noticed that you mentioned a large temperature difference between the 2 tanks. A 10C difference is a big adjustment for the fish to make. How long did you allow the fish to acclimatise before letting them free in the second tank?

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