Backyard Aquaponics
A place to discuss aquaponics

Well it's as the old saying - one man's septic tank is another man's sump...

Very clever.

My Rainbows weren't very hungry over the last few days but test results each day showed zero nitrites and close to zero ammonia.
Today I found two floaters. I tested the water and the results again showed zero nitrites but slightly elevated ammonia - not enough to be lethal, I'm sure, since my system normally tests at 0.25.
In the 2012 and 2013 seasons I experienced a few fish deaths after periods of extended heavy rain. There has been intermittent heavy rain for the last few days up here and I am wondering if this is a continuation of the pattern that seems to have established itself.
Has anyone else experienced otherwise unexplained trout deaths after fish tank inundation from rain?

Check out greencorevolution in phillipines. He is a big passion fruit fan.

http://www.youtube.com/watch?v=lKzVo4LO2OY

http://www.youtube.com/watch?v=iNMXH2rK4qU

Really impressive.

He also has a concrete fish tank.

Yep, Ive lost trout after rain and Ive read of others too. I never worked out if it was water run off from the gutters (not your situation), or a PH swing (also probably not your situation). Not a very helpful post I know but thought Id add my experience.

Sorry to hear of the losses, never fun. If they were floating they may have been in there for a number of days?

They were floating, Charlie, and another couple have since joined them as fertiliser.

As far as the gutters are concerned, there is a down-pipe that discharges into the tank, still connected from a generation ago when this tank collected and supplied water to the (shed) residents. I have never actually seen it discharging into the tank, although I don't make a habit of hanging around the AP area when its raining heavily.

I have left it in place because the dilution of the brown-stained groundwater in the tank by the rainwater affords me at least some visibility of the fish. This luxury isn't worth the loss of fish though, assuming the flush of rainwater from the zincalume roof is the culprit, so I will redirect the down-pipe right now - well, as soon as I have finished my coffee.

Thanks for the tip. I now have one less variable in my Unexplained Fish Death (UFD) equation.

Was there any thunder associated with these events. I have lost the occasional one or two after such "storms"

Oooh! a mystery, I love it.

Trout are very sensitive to oxygen levels.

Sudden barometric pressure drop would cause a corresponding drop in dissolved gasses in the water. If your water DO levels are less than saturation this might cause fish death or alternatively the suddenness of the fluctuation may be outside the ability of trout to cope.

If you know a low pressure weather system is approaching perhaps auxiliary aeration for the duration of the event might stop these weather related trout deaths.

Perhaps, but even an extreme case of a 20hPa drop in 12 hours is only a drop in pressure of under 2%. If DO was that critical, you'd be losing fish every day as the water warmed up.

In a fish tank that size and that much surface area, as well as low temps, I doubt 02 would be an issue

No thunder that I was aware of, Matthew.

I have a blower - a Sunsun 'Whirl Charging Aerator' - set to come on each evening at the same time as my bug zapper and they switch off around sunrise. The blower aerates the FT water via several large airstones that are hanging around the sides of the tank. These airstones, combined with two lots of filtered return water splashing into the tank as well as ~43 sqm surface area should provide plenty of aeration. Plenty may not necessarily be enough, however, and it may be possible for local factors to conspire to create particular set of conditions that result in a significant reduction in DO. I don't know the answer but I fished out another half dozen corpses yesterday before leaving for Perth overnight.

I am now back, there is a beautiful cloudless sky and the trout are as hungry as ever.

I had my rain water tested a while back for zinc. Its stored in a poly tank though is collected off a zincalume roof. Zinc levels in that were high enough to be toxic to fish.

PJ I think you should slow down on the beans. The seismic shocks from your thunderflashes are causing the fish to go into shock...

Very interesting, Matt; thanks.


Martin, thanks for your valuable and insightful input. I can confidently rule out your very worthwhile suggestion of a cause of my UFD, however, because all naked flames and known causes of sparks are banned in the AP area while I am in 'bean' mode.