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?
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.