Ahh. Got it. I'll definitely do a PH test on mine.
It wasn't in the tank.
I had one big sewer pipe going from the house manifold underground then up into the tank with a large screw cap at the lowest point near the tank. I took it off to drain summer rain and forgot to put it back on for a few hours. The Goanna must have gone in for a look and got trapped. I had the odd mouse come out when I drained that system but the goanna was a shock. Luckily I drain it down so often it was still intact, just a bit bloated and I had to live with the thought until it got diluted by time and water.
