This whole episode was unfortunate-- the large tank was built into a chimney breast and had been there for ever, long before we moved in. Fish had come and gone within it, but looking at it we said that if anything unfortunate happened we wouldn't replace either fish or tank. Sat night at about 11pm my OH noticed that the water level had suddenly and dramatically dropped. Knowing the water volume was pretty large we daren't leave it overnight, so set to to remove two dustbins full and dispose of it. Hence the fact that poor Haddock ended up swimming round a stacker box-- a bucket was a bit too small for him !