Aquaponics - Keeping good records

I had another fish death today, and it was after some rains. I had a niggling suspicion that the last one died after rains as well. There have been a lot of deaths and I now only have twelve.

I got some data from the bureau of meteorology to check against my records of fish deaths. Unfortunately, and foolishly I don't have complete records of deaths.

I had planned a good news aquaponics story today as the fish were all looking good, and feeding well over the last few days. I thought perhaps I'd put this fish death business behind me, so I figured I'd take some video to show how vigorous and healthy the fish seemed. I didn't notice the dead one. Not so vigorous.

Not recording those previous fish deaths was really crazy. My excuse at the time was that there was no point. It turns out keeping good records is incredibly important. If I had done so, I might now be certain of the cause of all my woes.

Here is a graph showing what I think is a correlation between my potential pH changing events, and my fish deaths. Fish don't like sudden changes in pH and a change can be fatal. Rain could have the effect of lowing pH, but I'm not sure if it could lower it, and then have it recover to normal levels before I did my pH tests. I'm also not certain if a short term change would distress the fish. After all, rain is pretty normal stuff in a fishy world.

B,D, and F all show strong correlations between rain and fish deaths. Rain would have a lowwer pH than my fish tank water.
A shows fish deaths in a dropping pH environment. Not due to rain, but due to the normal action of the nitrogen cycle. G shows the effects of the addition of shell grit to the system as a pH buffer to attempt (successfully) to buffer the system against sudden pH shocks.
C and E show significant rain events that may be responsible for my un-recorded fish deaths. Poor science I admit, but it was around these times that I lost fish, and I'm running out of other ideas. Did someone say "grasping at straws" ?

A,B,D, and F, all show potential pH lowering events. Sudden drops in pH can cause fish deaths. All my fish deaths I have on record strongly correlate to pH drops, or potential pH drops. Thats good enough for me to take action on.

I'll build a cover. It wont do any harm If I'm wrong.

On a lighter note, here is the happy fish video.