Please don't beat yourself up over it, it sounds like Al was just near the end of his lifespan. You certainly didn't do anything wrong, and it sounds like he enjoyed his time with you.
The most difficult part of being an octopus owner is the short lifespan. It's seems like things are going so well, and then they slip away. Sorry for your loss.
RIP Al and Saltador. The slow decline of your octopus sounds more like senescence rather than your husbandry skills. It is heartbreaking that they live such a short time.
R.I.P. Al and Saltador. We will all miss you. Sounds to me though like you didn't do anything wrong, just that when you caught him, he was already at an old age.
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