Backyard Aquaponics
A place to discuss aquaponics

Ok, so we converted our IBC. It had previously had magnesium hydroxide in it and we scrubbed it clean. We filled it with rainwater, added some pond water and plants. Checked the pH which was 7.5 so adjusted that.

We got our 12 trout on Saturday (round trip of 700km, no one nearer). Check the temperature and pH. Temperature was a bit high so left fishes in bag to adjust, then released them. First mistake, lost some as not enough air in water in bag pH starting to drift upwards again, lost another fish - jumped out, so made IBC escape proof. Adjusted pH by adding HCl diluted in water from IBC. Checked pH 7.5, temp 19.5C, ammonia 0.1 mg/l, nitrate 7mg/l nitrite 0.

Sunday after noon, more fish dead. Monday morning last one seccumbs. So I need to try an untangle what has gone wrong. Here are a few of my ideas, not sure what order to tackle them in...

pH too high, tried to change it too quickly ? (I know you're not supposed to do this by more than 0.2 per day) is the drift caused by the remaining magnesium hydroxide?

Something toxic in rainwater eg zinc? How do I get this tested? Anything else in water I've not thought about?
Why were nitrates so high? Was there something on plant roots (they were washed before planting)? Was the concentration I had toxic at that level?

So where so I go from here? I think I should try to get the water checked for zinc and if it's there I'll have to use tap water (which is chlorinated and fluoridated. Chlorine I can get rid of with standing in sun but what about fluoride?)
Try to get the system cycling before I get the fish? Use seasol? (I'm in Aus).

Other thoughts from the experts please?

Ouch, not a good start

Water readings look ok. Not sure how trout react to ph changes, hopefully one of the more knowledgeable pipes up. some died in the bag... maybe lack of O2 damaged the rest of them and this was the cause?

Doubtful about zinc causing the deaths that quickly, would have to be a very high reading I would have thought to do that. Tap water is probably preferred to rainwater due to the long term issue of zinc building up.

For fishless cycling, seasol powerfeed or charlie carp seem to be the two most use in Australia.

Sorry to hear about the fish. While it's possible it was a toxin I think the most likely cause was one of the following, lack of oxygen, ammonia or temperature. The damage was probably done in transit and they just died off over the course of a few days.

Yea my money is on temp in the end but they probably were well on their way with lack of 02.

Best to cycle first and make sure the system is reasonably stable and able to handle the load when you introduce your fish. It sounds like your trout were stressed and oxygen-deprived from the trip and waiting in the bag, and then couldn't handle something in your system, whether it was pH or the adjustments or an ammonia spike from it not being fully cycled. If you don't have a fish supplier closer then your fish will always be stressed on arrival (there's ways to reduce travel stress, but that long a trip is going to be hard on them even if you do everything possible to compensate) so you've got to make the environment they're going into as welcoming as possible.

If you're worrying about zinc in your rainwater, are you collecting it off a galvanised roof or something? That could do it all right...

Thanks for the info, very useful. Will get stare checked and then cycle fish less. This will probably mean I won't be able to grow trout this year though

It might be easier to start with bomb-proof fish like goldfish. They're a lot less touchy in their requirements, so you can get the system mature, learn what changes and how to handle it, and get a good backup of data on how things behave so you know what's normal and what's not.

I'd like to try trout some time, but we've got a really short season where they'll be happy here; I can look up weather records on the BOM website but that doesn't tell me what water temperatures are going to be like in my system. So I've got my mini test system running with goldfish, and when I get my big system built (soon!) I'll cycle it with goldfish, then switch to silver perch. They've got a much more forgiving temperature range than trout, so I'll run them for at least a year and keep records; by the time I've got good data on when it's safe to stock trout, my system should be fully mature and I'll have had a lot of practice (and probably a few Holy Shit moments). Of course, me being me, I might decide I like SP and don't want to change.

Mel, it's generally warmer here than Canberra, and I successfully raised my first batch of 80 trout in 2013 with ~8-10cm fingerlings only going into the FT in early June. You should have no problem, providing you have it set up so as not to absorb too much heat in spring.

Sonial, in my experience trout will handle a greater than pH1 change over a couple of hours with no problems at all.

My best guess for the deaths is lack of Oxygen causing brain damage, leading to deaths over a period of time. That has happened to me when a pump failed- they don't all die at once.

What roof surface material is your rainwater collected from?